[SOLVED] Unable to install or uninstall any apps (while processing: rsyslog-mysql)

I seen this topic closed without solution about problems installing apps since upgrading ReadyNAS OS to 6.7.4 or later.

When try install packages by shell error returned is: Errors were encountered while processing: rsyslog-mysql, and is not possible update or remove rsyslog-mysql due to the same error.

I solved this with:

sudo apt-get autoclean
sudo apt-get autoremove
sudo apt-get clean
sudo apt update
sudo apt-get dist-upgrade --fix-missing

**** Topid said: *****

This issue has been going on for quite a while now, through multiple OS updates. Currently running ReadyNAS OS 6.7.4.

I can't install or uninstall any new apps via the admin console. It seems to download them just fine, but when it's working through the actual installation process it tells me it's unable to install or uninstall the package.

Mainly, I'm trying to update Plex. Even downloading from the Plex website and uploading via admin console, it says it can't install the package. I've tried restarting, I've tried waiting for the next OS upgrade... nothing.