VCR Magnavox MWR20V6?

My unit keeps powering off. The display shows that there is a cassette loaded when the cassette carriage is empty. Sometimes it will load a tape, run for a few seconds and shut off. When I turn the power back on it ejects the tape and shuts off and still displays that the tape is loaded. I've hand cycled it from the full eject to the fully loaded position and back again. The start and end sensors and reel sensors are all working. The capstan seems to be working as well. I've taken the diodes and sensors out of the unit and checked them. They all function properly. Could it be the mode switch or the IC control module? And, how can I know which it is for sure? I've had the unit completely disassembled. This is no easy task, but I am determined to fix it myself. Someone please help me.