Do you have and have you tried the original firmware version; 243_23_31?
Off their FTP site;
I haven't, no. I may have that one downloaded already, if not, and I need it, I will. It's been behaving 100% normal again, recording everything so far, nothing missed. Seems going weekly for recordings and not doing Mon-Fri, cut out a lot of the problems.
My unit does record and play at the same time, had 2 recordings going and was watching a third. The problem most likely is in your storage media, memory sticks are junk for recording to, SSD USB drives on the other hand, are the cat's meow.
I did something similar, I did 1 program for Monday to Friday set Weekly. Setting it daily would be a hassle. Since all of my programs are weekly, this way, there is no corruption with other types of programs. Just meant more work to set it up.