Sounds like HDD issues. They start with random missing files and then causes a domino affect to other files/components/programs. Usually a good visual sign is task manager if your memory is constantly over 50% ( normal usage is around 29%-39% ) then the OS is trying to repair bad sectors but eventually those sectors become bigger and worse and the OS allocates more ram to repair until it crashes.

Ditch the old HDD. Invest in a PC that can be used with SSD.

I have a few of these products, surveillance cameras, door cams and smart light bulbs. But a lot of spy mintuar cameras are also made and shows up as that company. I had a USB charger that doubled as a spy camera so they could be hiding in vents. There is a few phone apps that detects them easily which you can try or turn off the lights to each room, put your phone in night vision and scan area for bright dots.