I had remotes that stopped working due to residue/flux left around ceramic resonators and adjacent parts. I suppose the residue became conductive just enough to disturb the clock signal, and the remotes stopped working. Now, when I open the remotes for whatever reason, I always check if the PCB is clean.
I've had a certain series of Sony VCR remote lock up (dead) and the only fix is to remove the batteries for as as long as 7 to 10 days or heat the PCB to around 70C for a few hours. Even wrapping the the board in tin foil to remove all charge doesn't work. Definitely the most obscure RC fault I have encountered.