I'm having the strangest of issues and can't figure it out for the life of me. I designed a custom add-in for Solidworks PDM that allows a user to create a report and attach references to the report. Normally when creating the report, the user is first prompted with a windows form to enter information. There's a "Paste as Reference" button on the form that launches the add-in when clicked. On some computers, the add-in behaves gloriously - when you click the button an Open File dialog window appears, allowing the user to select files in the vault they'd like to include as a reference. After selection, the add-in proceeds to create the report with the reference files attached such that they appear under the "Contains" tab when viewing the report in File Explorer. The issue I'm having is that on Computer A, User 1 logs in with their credentials and it behaves as expected. On Computer B, User 1 logs in with the same credentials and the add-in behaves differently. It causes the Open File dialog window to open twice (click the button in the form and it opens, then click cancel/open in the Open File dialog and it opens another dialog window on closing) and the add-in creates the report but doesn't complete the final step of checking the report in. 

I don't fully understand PDM, but I'm narrowing it down to something about PDM and not the code for the add-in. I've analyzed the code for the add-in several times and there's nothing that would cause the Open File dialog code to be triggered a second time. Either it would happen an infinite number of times or just once (as intended). So, to me, PDM is doing something to interfere with the add-in. But how to get to the root of the issue, being it works for a given user on one computer and not the other? Where should I even begin searching?