Top and bottom screws on tablet not staying in place after removal?

I attempted to disassemble the tablet to clean the fan. I stopped midway as I couldn't get the side screws (under the joycon housing) undone with my small philips screwdriver. Now I have replaced the 4 screws on the back, but I could only manage to get one of the very small black screws on the bottom back in, and the other bottom and single top one are just dropping into the screw cavity and turning but seemingly without biting anything. Have I somehow stripped the screw thread on the inside...? The screws themselves look fine. How can I get these to stay in, I don't want to get more dust inside my console. I would consider loctite threadlocker on a bigger screw but this seems too fiddly for that. Thanks in advance!