Sorry to hear that. I think the following happened. The RME device was most likely in submix mode. Turning down faders has only effect on the "submix" (which is per selected hardware output channel).
The 1st thing before actual use is to ensure proper listening levels like you would do with analog mixers and monitors.
If your monitors have a volume knob then it is easy to ensure that.
If your montors dont have a voume knob then you have simply to be careful (use of monitor controller or 1st to use phones only and speakers finally if you have setup the TM FX mixer.
IMHO .. The only proper solution for monitors without volume knob is to get either a monitor controller or smth like a passive dampening element. Because .. its too easy to come back to 0dB by double clicking to the Main Out fader "by accident". As a double click toggles between max volume and your previous volume setting.
A good monitor controller is i.e. this here: https://www.thomann.de/de/spl_2control_black.htm
I personally turn monitors down as much as possible, that even a 0dB signal can't fry anything.
I keep a little volume reserve on top for listening music by using "gain tag" information to have an unique listening volume.
If you need further assistence, then look at my guide.
I added now a warning note to adjust volume levels on speakers before 1st use to be on the safe side:
http://www.tonstudio-forum.de/blog/inde … rnal-equi/
Also good video tutorials about TM FX capabilities here:
http://www.tonstudio-forum.de/blog/inde … al-Videos/
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14