The fact that three different versions of Acrobat are showing the same problem potentially points to something outside of the individual Acrobat installation as the source of the problem. Here are the things I would try:
1. Run a virus scan on your system
2. When a simple re-install does not fix a problem, it's time to use Adobe's "Cleaner" tool to wipe the system clean in regards to any traces of Acrobat: Download Adobe Reader and Acrobat Cleaner Tool - Adobe Labs
If this still does not fix the problem, I would get in touch with Adobe's support regarding the problems with Acrobat DC: http://helpx.adobe.com/contact.html (don't use any of the "Forum" options, otherwise you will end up here again)
Do you have three different versions of Acrobat installed on the same computer?
no i do not, when changing to differnt versions i fully uninstalled the previous
Has anyone got a fix for this besides the cleaner tool? Or has the cleaner tool been working?
I have a user with the same problem, that just started yesterday - uninstalling/reinstalling Acrobat DC or running a repair on DC has not fixed it. I can't use the cleaner tool, as it is for standalone versions of DC and we have an Enterprise install. If the user converts Word 2016 files (.docx) to PDFs first, then she can combine the PDFs ok, but that's just a workaround. Help!