I have a vBulletin server running (v4.2.5), with PHP 7.1. They were running on the 10.1 version from the apt repositories from Debian (mariadb-server-core-10.1/stable 10.1.38-0+deb9u1).
I decided to upgrade the MariaDB using the MariaDB apt repo, which gave me an upgrade to 10.3.14.
The database is replicated onto another server with the same OS / MariaDB version from stratch (Debian 9 / MariaDB 10.3).
Replication works fine :
Now, whenever someone opens multiple threads in a very short time range, they will likely be facing a "Database error". As an admin, I can see what the error is, and I can guarantee that this wasn't present when the database used was MariaDB 10.1.
I opened a thread on the vBulletin support, but they told me there shouldn't be any issues on this type from the version I'm using, and they don't test every MariaDB version so they can't confirm the problem.
Is any help possible here ?
Here is the error I'm getting when it occurs :
(I masked the IPs)
Tables are running in InnoDB for almost all the tables (the issue also occured when they were in MyISAM).
Could this be due to replication ?
Is there anything I can provide to help fix this ?