I have a series 3 HD TiVo that I receive OTA channels with an antenna.

Last week while changing channels, I lost video and audio on all channels. The TiVo banner was present but the picture was black. I could still watch recorded programs, but not live TV. Restarting the TiVo solved the problem, but I lost video and audio again about an hour later. I noticed the case of the TiVo was very hot, the internal temperature was high and the fan was not spinning. I set up a floor fan to blow air directly on the TiVo and the next morning the internal temperature was within the normal range. Without restarting the TiVo from the previous night, the video and audio were working properly. I ordered a new fan from weaKnees, but in the mean time I continued to use the floor fan and I did not have any additional issues for the next three days. I installed the new fan, but within an hour, I lost video and audio. I restarted the TiVo and the video and audio are back, but I suspect the problem will persist. Do you have any idea of what could be wrong?