Randomly over the last week my quad has started to act strange. For example I'll fly around a bit and then land and maybe talk to a friend for like 30 seconds while it's sitting on the ground disarmed. Then it suddenly starts making the last 2 beeps as if I had just plugged it up again or sometimes only 1 beep and then my taranis reads something like 15-17v ( and this is on 3s so there's no way in hell lol ) and seems to freeze up like that and it won't arm or do anything. I have to unplug it and turn off taranis and back on again and sometimes it just does that immediately again, or will display RSSI but no voltage at all and be unresponsive. It's happened a few times over the week but tonight I turned both off and back on 4 times and it wouldn't ever stop doing that. I left both off for a few minutes and tried again and it connected and was working as normal again. No clue what the heck is going on

Sounds like something is getting too hot.

It's hard to make more than a guess without seeing some pictures of how you have put everything together, but maybe your VTX is causing other parts of the quad to overheat.

it's a 112m size micro with the 4in1, fc, rx all stacked on top of each other. the Rx is super close to the fc. the vtx is on other side of the carbon and doesn't seem to get all that hot on 200mw now that it's cool outside. I mean maybe the rx is getting some interference from the fc, but that doesn't make sense because I've had it built exactly like this for months and never had a problem.

There's only really two explanations for a fault like this but it can be hard to track the fault down without painstaking effort.

Either something starts failing when it gets too warm or you have a bad connection somewhere. The only way to really diagnose the problem is to take all the electronics off the frame and have it all connected together on the bench. If it doesn't go wrong on the bench, start hitting each circuit board with a hair dryer. If you warm a board up and it stops working, you've found it.

Bad connections can be invisible, especially the kind of bad connection that happens on soldered wires. When you solder a wire, the solder wicks up inside the insulation. Where the solder stops and the wire begins is a weak point and if any of these wires are subjected to constant movement from prop wash or vibration, they will eventually fail, inside the insulation where you can't see it. Give every wire a gentle tug to see if it causes a problem.

Whelp, I tore it down and resolder'd everything just in case and tested it. Seems it's just the flight controller that's screwed up. It won't even stay connected with usb. It connects and then like 5-10 seconds later just disconnects. I managed after 20 mins of fighting with it, got it to stay connected and flashed it full chip erase but it didn't help any. Guess I'll msg furiousfpv and see if they will replace it considering I've bought 5 piko blx's and 3 of them burnt up randomly, one time causing me to lose my entire quad. They could at least send me a new f4.

I hope they help you out. You wouldn't be the first person I have heard of with multiples of these boards having problems. The Piko BLX has a really thin PCB, so any kind of twisting or bending will bend the components and cause them to fail.