RME did release a firmware update that reduced/fixed that problem, as I recall, if this is your problem. Fortunately my ADI-2 DAC FS that I bought a couple of years ago never had that problem.
Another issue is with some units of the ADI-DAC FS that uses the ESS DAC IC have a high frequency tone (10 kHz+, if I remember correctly) that can be heard by some when the screen has a certain brightness. There is a simple hardware fix, so you'll have to send it back to RME or one of the distributors.
In any case, RME don't abandon their users to their own devices. All manufacturers have some issues and it's important how they deal with it.
Firmware Update ADI-2 DAC 66 / 47 and ADI-2 Pro 259 / 111 (Page 1) — ADI-2 & 2/4 Pro series, ADI-2 DAC series — RME User Forum —
forum.rme-audio.de
>>>
Encoder jumping and direction errors: This firmware includes a new logic unit that intelligently detects and eliminates encoder switching contact errors. In addition, there is a variable filter with levels 1 to 5. Default is 1, which is largely similar in feel to the previously used filter. Higher values lead to an attenuation of very fast changes. Strongly jumping or backward running encoders can in most cases be used normally again with the setting 3. Very fast, short rotations can be replaced by medium-fast rotations after a short period of familiarization.<<<