Garbled text intermittently on PDF

I work for an IT support company that is experiencing this issue. I have found the same issue in a few different posts.  Example 1 Example 2 

Users will download documents from a website, and the pdfs work almost all the time but then (seemingly) suddenly, don't. I thought I had found the cause of the issue, as one of the vendors they have to download pdfs from, their site only works in Internet Explorer. When they opened the file in Internet Explorer, it opened an instance of Reader inside of IE, and every file after would come back garbled. To correct this behavior I went in and disabled the Adobe add-on for IE. Located under the "Start without permission" section. This seemed to have fixed the issue for almost a week, but then my primary user with this issue let me know that they were experiencing the issue again. They can get the document (the exact same file that was downloaded previously) to open correctly after a reboot, but once the problem starts any document that was previously working, is now a garbled mess.

I have checked the font, Arial Black, which is a Windows default font so there should not be an issue with the font unicode or anything of that sort. There are also users with the same documents and same version that that do not have this issue.

While the problem is occurring, I can open the same file in Foxit Reader, or Edge and the document opens just fine. This would be my solution seeing as the problem is solely with Reader, but the other readers format the document slightly different and does not force it into a portrait format for 8.5x11 paper and instead prints it in landscape to fit the document better. I could potentially get some more advanced printer drivers and fix this, but why would Adobe not just work like it is supposed to?

I just spoke to another user having the same issue, but today they had a strange variant of this where the second page of a document was garbled, while the first page was fine. Later on, the exact same file was opened on the same computer without restarting or anything and the second page is now fine.

I chatted with someone here at Adobe that suggested trying a document that I knew the origin of (created using Adobe Acrobat Pro XI) which I have not been able to test yet, but this doesn't seem like a very helpful troubleshooting step overall.

I understand this is a free program, but the program should at least work.

Will include screenshots as I can get them.