My sBITX (#59) has been acting strangely, too, and I think the problem is the supply voltage.? I've taken some measurements at J3 (digi board) with various components attached.
The voltage at J3 without the Pi or touchscreen is 5.40v.
Plug in the Pi (and external HDMI monitor) and the voltage drops to 5.25v (CLI display) and 5.21v (GUI display).
Add the touchscreen and the voltage drops to 5.01v (CLI) and 4.98v (GUI).
Running the sBITX software (GUI) the voltage drops to 4.94v and stays at 4.93-4.94v for several hours.
When the screen blanker kicks in the voltage increases to 5.13v.
Other units may perform better or worse.
The Pi 4 wants 5.2 to 5.4v and misbehaves with lower voltages.? The LM388 can supply the necessary current but R79 and R80 (main board) may need adjusting to supply 5.4v under load.
-73 de Paul? K9MV
