Is your DEBUG.LOG empty (after enabling debug to a log) ?
Is that clean ?
Also as Robert asked, tell us how PHP memory you have allocated, PHP & Mysql version (or type).
Yes the debug log is empty and says there are no errors in the database. My sql version is 5.5.5, php version 7.1.30 and php memory limit is 2568m. I can give you access to my site so you can look into this properly. The forum has worked fine for the last year so I don't think its my host.
If that's the problem how come its worked perfectly for a year on the same host?
Still not been able to fix this issue. My host provided me with this info with regards to mysql version - Server version: 10.2.25-MariaDB-log - MariaDB Server
The versions of MariaDB are identical to MySQL through version 5.5. It offers all of the MySQL 5.5 features. After version 5.5, MariaDB versions start at 10. This is to indicate that not all of the features from MySQL will be imported. The current stable release of MariaDB is 10.2
They also said the database is using InnoDB
thanks for your reply but it would be good to get a reply from some official support