Visio 2016 crashes and export PDF issue

[visnny]

I have a Visio add-in that is built by using VBA and VB6. My users always complaint that their Visio 2016 crash when they are using my add-in. The worst case is one of the users is facing the crash problem for each 15 minutes. Also, sometimes VBA is unable to load after crash. However, the action that causes Visio crash is random, therefore I am unable to figure out the root cause. I've attached the error log.

Another problem is, when my user is trying to save one of his drawing as PDF format, Visio will crash. This only happened on certain drawings. After I've reconnected some connectors, then only he can export the file. I've attached the error log too.

Any ideas?