If that doesn't work, try resetting the Workspaces: Reset a workspace Reset the current workspace to return to its original, saved layout of panels. 1. Do one of the following: • Click the Workspace menu icon and select Reset to Saved Layout. • Choose Window > Workspace > Reset to Saved Layout. from here: https://helpx.adobe.com/premiere-pro/using/workspaces.html
If that doesn't work, try Preferences > Audio Hardware and set Input to None.
If that doesn’t work, try updating or rolling back your graphics driver directly from the video card manufacturer’s site.
If that doesn't work, try creating a new project and import the old one into it.
Same problem here since 14.6. Since Adobe doesn't seem to care about this problem, I decided to investigate it myself. It seems that this bug could be related to control surfaces. I tried to remove my 2 control surfaces (BCF2000 & Loupedeck+) and I can add tracks again (I haven't tested the other bugs any further. because I need my control surfaces)
As soon as I got a control surface declared in Pr preferences, it crashes every time I add a new track.
Please Adobe correct this ASAP. Going back to 14.5...