Occasionally has difficulty decoding packets

I've noticed this specifically with the 4" Square Display (https://www.adafruit.com/product/5808) and the Qualia ESP32-S3. It will work most of the time, but if let sit long enough (maybe 5 minutes or so), a runtime error will occur:
```
Traceback (most recent call last):
File "code.py", line 97, in
File "adafruit_focaltouch.py", line 137, in touches
RuntimeError: buffer size must match format
```

Also, `code.py` is just https://github.com/adafruit/Adafruit_CircuitPython_FocalTouch/blob/main/examples/focaltouch_paint_rgb666.py with the try and except lines removed.

Start with adafruit_focaltouch.py at the touches method and compare its packet handling with examples/focaltouch_paint_rgb666.py. Reproduce the failure on the 4" Square Display and Qualia ESP32-S3, then determine what prevents the buffer-size runtime error after the device has been idle.

Written by the indexing model from the issue text.