Adobe Acrobat DC customize the forms

[Bonmboso255342473lh6]

I was doing support for a client recently and they told me this:
In Adobe Acrobat Pro, if one of us wants to customize a form (PDF), the font always jumps to an unreadable font and setting the font to standard Arial has not improved things.

I tried this solution already

[try67]

What exactly do they mean by "the font always jumps to an unreadable font"? Also, what tool are they using when they are making these edits?

[Bonmboso255342473lh6]

I had a meeting with my boss today. The client has described the situation and my boss has been able to recreate it, but when he showed me it seemed fixed... Still, I'm gonna update the symptoms a bit:

Apparently, they would both try to edit textfields in Adobe Acrobat DC Pro and when they tried to type in something the font style would automatically set itself to a .tmp font style even after changing it back to its regular style. 
But, as I said, today we were not able to recreate it...