Experiencing something similar and tried the same solution from the other thread as mentioned by the OP.
Just tried pihole -r and get this message:
/usr/local/bin/pihole: line 69: /etc/.pihole/automated install/basic-install.sh: Permission denied
Are you running the development branch?
What is the output of
ls -lhs /etc/.pihole/automated\ install/
Run a pihole update again. A fix was pushed.
https://github.com/pi-hole/pi-hole/pull/4368#pullrequestreview-771737634
I run dev branch indeed.
Looks like it was solved, I just swapped back to master and then back to dev, probably just after the fix was pushed.
Will check with next updates and see if the issue is gone.
Thanks!