Topic: Direct USB Recording with external hard drive - beware vibrations!
This falls into the category of "I should have known better" but I wanted to pass on information in case it helps others. I tried using the UFX for the first time as a mixer for my band last weekend. I had the unit in a rack with pres etc. on stage with us, and was able to run 4 mixes (FOH, foldback, and two stereo IEM mixes) from my iPad using Touch OSC. It worked great! Not as good as having a dedicated sound guy out front, but for a small gig where most of the FOH mix is just vocals it worked very well.
The only problem I had was with recording. I decided to record the session using just the DUSB function as a test. Fortunately we were not relying on having a good recording of the gig. There were many, many errors throughout the recording that resulted in the audio skipping repeatedly. After a little investigating I realized it was because the external hard drive was affected by vibrations on the stage. Whether is was mechanical vibration through the stage itself or perhaps the bass notes resonating the drive I don't know. I do know that I will not use a spinning drive for this purpose in the future, but instead use an SDD or fast USB flash drive.