ADB PULL (of app_pocess) fails with exit code 1
The cause was surprising, but poor error reporting even more frustrating.  My devices is connected using USB, passed through to a VM.  It seems USB timing issues cause the connection to be intermittent or out of spec.  But not enough to cause an error in system log.
abd do not complain about the latency or loss of connection, just quietly died with error 1.  Switching to a TCP connection from USB resolved the problem