Complex formulas are typed up in Latex for maths research and PDFs are created. We do some editing in Adobe Acrobat Pro afterwards to the PDFs. This was working fine until a few months ago.

Symbols started randomly disappearing from PDFs. The same symbol in the same article disappears in some cases but doesn't in others. We have tried fixing the font problem in case some fonts are not on our version. We never know which documents will have a problem and which ones won’t. It’s random and mysterious.

It's not a simple case of missing fonts or outdated fonts or something like that. We've tried plenty of things but still, the symbols randomly disappear in some cases and not others. It seems like a bug and maybe it can be fixed in the next update?