Cant turn off Transmit Device Playback, says Invalid type conversion, 25.3.0 beta

Good catch, yes, I was going to look for this thread to let you know.

BTW: I use the "/" in the numeric keypad as it's the same in After Effects

Yes, that's right. It might have taken your update to the prefs, just open it up and check. I believe that error comes up whenever you press the <OK> button, even if no changes have been made. We could use an <Apply> button there, but the prefs would have to be a non-modal dialog to gain the maximum. But even saving more than one pref on different pages, would benefit with an <Apply> button. FWIW: Here's how I have that pref setup, while using a keyboard short:

I see, so its not related to Transmit, its you can't click OK at all, I did not try any other setting changes, that was all i needed to change. 

In premiere beta, I clicked Help and Provide Feedback, and it took me to this forum, I thought this was the right place then. 

Will watch for another update 

will have to try that shortcut also thxx!

BTW: You can create a keyboard shortcut to Enable Transmit: