I had a Fresenius K machine that none of the front panel buttons were working. I swapped the panel out with a known good one and it worked fine.
While waiting for the replacement part to arrive, the same problem happened again on the same machine. It worked for a week.
Could it just be that the second panel failed also, or is there something else going on with this machine that can be checked.
Any thoughts?

I would check the front panel interface board and all the cables going to the front panel.

I agree. Had a K a few months back was doing the same thing. Fresenius replaced panel under warranty which seemed to cure the problem for about 2 weeks, then problem returned. I replaced the interface board and haven't seen the problem since. Fresenius Tech did say if the interface board did not fix the problem it may be the cable or Function board.

Another option take a quick look at all of the buttons on the front panel make sure you don't have any buttons mashed in by the staff. If you have a button making constant contact none of the buttons will work