Weird Squares / boxes replacing text when combining PDF's

Hello, recently I have had a couple members of staff report an issue with Adobe where in combining PDF's , it replaces some text with weird squares / text boxes (See attached for example).

I have scoured every possible fix and troubeshooted it as much as I can as the issue is replicating on my own machine, but unfortunately, I am at my wits end. 

Other users seem to be having this issue but there never seems to be a fix that has worked for me that I have seen on the Adobe community, so far my troubleshooting has narrowed it down to: the only parts of the document that get's re-arranged are the parts in the Arial font or some varitation of Arial. I have installed every possible Arial font to my device, reinstalled Adobe multiple times as per advice but I still have the issue. I can fix it by going into the document, highligting the weird text boxes and changing the font but obviously it isn't a great fix as some of our PDF's are 400+ pages and it's too time consuming.

Any help would be really appreciated.