> Does anyone have any idea what might be the issue at all?

I am also an RME customer and own this audio interface UCX II, which can also be used very well as a heat pad in winter.

I'm afraid, that the room temperature is too high.

If your room temperature is already for example around 30 degrees Celsius and more, you have to add this temperature to the device temperature, regardless of whether it is an audio interface or a PC.

Fans that you may already have installed will not help you here, as they only circulate the warm ambient temperature in the room. Therefore, only an air conditioning system that can lower the room and its device temperatures will help with such devices.

a fan does not work like an air conditioner and does not lower the ambient temperature, but it does cool electrical appliances by rapidly dissipating the hot air from that appliance. So fans do help.

Your firmware version?

That's a bug, thanks, will be fixed.

UCX II is on firmware 42 right now. Also check power supply and USB cable.

I still have the same issue with UCX II. I can't pinpoint exactly why it is happening but here is typical scenario:
During playback I decide to switch from studio monitors to headphones.
1. In TotalMix I click on "Phones 1" strip and raise the fader (Software Playback)
2. then I raise the fader on "Analog 1/2" strip (Hardware Inputs). but my headphones don't produce any sound.
3. Both signal indicators show the signal, however no signal goes to headphones and the screen on UCX II doesn't react to configuration change.
4. If I bring Main fader to a minimum (or mute it) the signal still goes to my monitors, not to the headphones and UCX II OUT indicator is frozen.
5. At this point any change I make in TotalMix has no effect on UCX II. and VOLUME knob doesn't work. I can't only shut down the UCX II forcibly by cutting down the power at my power conditioner.
6. After UCX II restart everything comes back to normal and all knobs/faders operate normally. I listen to monitors or headphones problem free and can switch between the two. If I change the volume the UCX II screen shows that immediately.
I cannot find repeatable pattern for this, it appears to happening randomly.
I also don't think this may be caused by power supply or USB cable connection as the playback goes absolutely clear without any hiccups or delays.

I am using original power supply and USB cable. All connections checked/verified to be 100% reliable.
OS is Windows 10
UCX II Hardware Revision 42
Driver v1.227
TotalMix v1.79

Does anyone have this kind of problem? ...and possible fix?

Or Cue pressed somewhere?

Update: March 26, 2023
Here is the sequence:
1. Playback trough studio monitors - no problem.
2. Headphones plugged in - TotalMix channel indicators show signal in both Main and Phones 1 channel (Hardware Outputs)
however no signal goes to headphones and UCX II screen is frozen (out level indicator doesn't move)
3. Rotary VOLUME knob is not responding.
4. Shut down the power and restarted the UCX II
5. After restart TotalMix FX message popup:

"Mismatch detected - channel and FX settings of Fireface UCX II (1) and TotalMix are different.
Click YES to use the TotalMix settings (default)
Click NO to upload the Device' settings into TotalMix
Note: If unsure click No to check the unit's settings first, then Hit Undo to restore the last TotalMix settings."

6. In TotalMix all ADAT channels (Hardware Inputs, Software Playback and Hardware Outputs) show OVERLOAD.
7. I clicked Yes in the message box and ADAT channels came back to normal.
8. Both monitors and headphones work as expected.

I still have no clue what can cause this weird behavior and would appreciate any help. Thanks

Can you post the serial number of the UCX II?

I can't find a serial number, but there is a barcode on the box with this number: 24072416.
Is that the one?
I found following instructions about how to find serial number:
"Open Totalmix. In the top right corner you should see the name of your interface, when you click on the name the number appears."
That doesn't work. When I click on 'Fireface UCX II' in the upper right corner a text pop-up shows the same name but no number.

Thanks, Matthias

There must be a barcode sticker on the unit showing the serial number.

I have checked that your unit is not one of the first batch that had soldering issues (which also showed up slightly different). Please contact RME Support for an in-depth analysis. There are too many variables and possibilities what is going wrong here. This one:
> 3. Rotary VOLUME knob is not responding.
together with the other stuff is basically impossible, the unit hangs, and this points more to a hardware error within the UCX II.

Are you sure this is the original RME power supply, and the DC connector is fully inserted and locked?

By the way, is it possible to check somewhere by s/n if my unit is in the  "soldering risk group" ?:)

Contact your local distributor, nothing else to do. This is warranty so you don't have to worry.

Hardware revision is not the same as firmware version!

Ah sorry, I’m wrong then. And as it seems it’s how you see it. Some devices exist with different hw revisions which require also different firmware versions. It’s the same with my Digiface USB for example. Of course in the case of the UCX II I mixed things up (although it’s still true, firmware and hw rev. aren’t the same).  I don’t know the differences between hw rev 6 and 7.

Thank you, Matthias! I just followed your recommendation and contacted my local distributor.
My problem was resolved fast! My FF UCX II unit was sent to GerrAudio (our local Canadian distributor) for repair and/or replacement.
I even got lucky to negotiate an upgrade. So, within 2 days I received brand new Fireface UFX III interface and it works flawlessly so far. (Of course I paid the difference in price.)
Thank you, Matthias, thank you AVShop.ca (local retailer), thank you Gerr Audio (local distributor)! Great people, Great service!

I received my UCX II a few days ago (HW-Rev 7, USB 106 DSP 26 USB (CC) 104), the screen briefly flashes 2x when I power on the device. Obviously this is not normal, because my other RME units do not do this. The connector is locked according to the label. No other problems found. In the long term, should this not be a problem? What do you suggest? Should I send it back to the dealer? The video is attached.

https://drive.google.com/file/d/1HGRH1L … drive_link

This is done when the electricity is applied, not when the appliance is switched on with button. I think it's obvious from the video and the description, I can't show both the appliance and plugging it into the power socket at the same time. I know that the appliance is turned on and off with the button. The question is whether it is normal for the screen to flash when electricity is applied to the device. And I have tried several power distributors, it is not the power distributor that is at fault. The dealer suggested that I ask the RME experts here, he says there are two things, either a display fault or a ram fault.  Thanks for all answers in advance! (Although I'd less like to be told, as I once was in a furniture store, to prop up the legs of a wobbly chair or cut off the other legs if I don't like the wobbles...)