I have encountered a problem with 2.1.20 writing to my public keyring.
I was using the pre-compiled binaries on Windows 10.
When editing/refreshing keys, or running gpg --check-trustdb, at the
end of the operation the command window gradually fills up with
repeated lines of:-
gpg: waiting for file 'C:/[path]/gnupg/pubring.kbx' to become
accessible ...
These lines keep coming until I close the command window, or CTRL C
then RETURN, or terminate "GnuPG's OpenPGP tool (32 bit)" in Task
Manager.
Oddly, creating new keys does not seem to trigger this (Or else the
problem is intermittent.)
The problem went away when I switched back to GnuPG 2.1.19.