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 "app_process". 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)