I just had a cheap clone Minim OSD board that suffered weird symptoms: Charset is always garbled despite multiple update attempts; Would only work for a couple seconds before showing “No mavlink data”; EEPROM read/writes fail a lot on configurator, “cannot talk to bootloader”, etc.
The problems only seemed to show when the board gets warm. The CPU still seemed to be running as “no input data” screen updates normally. Also, everything that didn’t work seemed to be UART-related. All these symptoms could be caused by a large enough error in oscillator crystal.
The new crystal. Solder pads marked in green boxes.
Replacing the crystal oscillator (16 MHz) seemed to fix all the problems despite the huge size difference. I’ll try to replace this oscillator with a SMD one before it sits long enough and earn the “if it ain’t broke don’t fix it” status.
Anyway, this is not to endorse the purchase of knockoff components - but if you’ve got a board that starts to show weird symptoms as summer heat begins to kick in, this might the culprit you are looking for.