I also have this very same issue, also with KP 50 and CSSU testing, but I am not sure what is causing it.
I do not have any problems with the USB connector, however I secured it using epoxy. But I don't think that is relevant because the problems started to appear a long time after I did that.

What usually helps is powering off and removing the battery for several seconds, until all capacitors are void of rest-electrons. You may try that. Admittedly it is not convenient since you have to set date/time again on bootup.

After a crash it is sometimes worse, rebooting several times until it works again.