ADB PULL (of app_pocess) fails with exit code 1 I am trying to pull a file from my phone (Blackberry Key2 / And 8.1) and it fails with exit code 1:
[host] admin$ adb pull /system/bin/app_process ./ ; echo $?
1

I confirmed the source file exists, and I have have write permission to current folder, and to /tmp, but it always fails for file &quot;app_process&quot;.  I tried pulling a simple text file from /sdcard/test/myfile.txt to /tmp  and that works.  So for some reason app_process won't pull!
I restarted adb daemon, confirmed phone is in developer mode (and all options permitted) , restarted the host (Mac), ran adb with sudo, etc.  No difference, and no error message.
I am running adb v1.0.41, version 30.0.5-6877784 on Mac OS
I saw this post that suggests it might relate to a symlink, but trying to pull app_process32 (which is a file) has same issue.
How do I solve or debug this?  (This command is part of the final build process so this command has to work)
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