Database locked error

Sonarr version (exact version): Sonarr Ver. 2.0.0.5322
Mono version (if Sonarr is not running on Windows):
OS: Ubuntu 18.04 LTS
Debug logs: https://pastebin.com/ENKLBuky
Description of issue:

Hi. Noobie here so apologies if this is an obvious fix or gets asked a lot.

I’ve installed PGBlitz on a dedicated server. I have been struggling to get Sonarr to work. The error states that the database is locked.
I found this: Sonarr: Task Error: database is locked which suggests that permissions to access nzbdrone.db are not properly set. Looking at the rest of the error this would seem like the issue. How do I go about giving Sonarr write access to nzbdrone.db (assuming this is the cause and fix)?

Many many thanks in advance.

Cheers,
TimmeH!

A quick update - if I use v.3.0.2.570 then I receive a similar permissions error:

https://pastebin.com/zS7WDhE4

More debug log files here after a restart, which will hopefully give more info to be able to identify what is going wrong:

https://pastebin.com/ye0YGL1a

Any advice or tips greatly recieved!