> upgrade vbulletin to 4.2.5
I was thinking why. because 4.2.0 worked on previous server so i would think version is not the cause. But i spend my time to upgrade to 4.2.5, but that NOT helped. Same error.

Do you get any other errors at the same time? Check server error logs.

The db error that you have posted in OP does not give any error information.

@iA1

thank you. I enabled debug mode

and visited the page that is reported having the error mentioned in the first post of this topic. This one:
http://mydomain.com/domains/mydomain.com/public_html/archive/index.php/f-43.html
(note that after move to a new server, site started showing bad URL in adress bar as seen above, but that is possibly another issue not related)
i am then redirected to:
http://mydomain.com/domains/mydomain.com/public_html/sitemap/f-43.html
where is the mentioned SQL error and thanks to debug mode, i see something more:

when i reloaded page, it shows without issue (so this looks like a random issue?). As you suggested i also looked after error_log file, but there was none in the sites root directory. But hosting control panel has access to error log and found errors like here.

If you're running vbseo, I highly doubt it's compatible with PHP 7 (because it hasn't been updated for many years) which is why it's throwing those errors.

My URLs was shows wrong: http://mydomain.com/domains/mydomain....php/f-20.html and that i should fix it first.
I ended up enabling vbseo plugin, going to admincp, vbseo, Settings, Options, Advanced settings and set DocRoot path there to be /home/myusername/domains/mydomain.com/public_html
Now URLs show up right and a few days i seen no MySQL error :erm: i think these URL things can also relate to .htaccess. I will report back if the issue re-appear..