MyBB Community Forums

I manage 2 forums, both on Mybb 1.8.21, but both on different hosts; the following only effect one of the forums - the other is fine

Today it has been noticed that some PDF files are apparently corrupted; any PDF uploaded (or has been uploaded already) that is over 1mb won't show properly; things are corrupt, and remains corrupt when I download it.  Really strange, as when you reload the page/ attachment, the corruption effects a different part of the document.  As such, I think the files are fine, it is just some issue accessing & displaying them

Any PDF under 1mb is fine, and everything was fine up until recently

Could this be something wrong with myBB or is it (more likely I think) something to do with the host?

The only tasks carried out recently was updating myBB to 1.8.21 from 1.8.20, and also my host an attempted to fix a problem their end by updating the site from PHP 7.0 to 7.2

Any help is appreciated

I don't think MyBB modify the PDF, peharps that changing the PHP version changes settings too. Have a look to your php.ini and to your logs (php errors, apache/nginx errors)