I chose to respond here, and the entire community can see it too.
First of all, thank you so much for your patience, I use the small script you gave me, which also sometimes works and sometimes doesn't.
After the bulid, the situation is also sometimes good and sometimes bad, and I'm still not able to find out what the reason is, but most of the bulid is normal afterwards.
It it still also sometimes works and sometimes doesn't, then something else (external to the Dialogue System) is stealing focus. Can you identify what other systems in your project could be stealing focus? Can you make a simpler copy of your project and remove systems until it no longer steals focus? This way you can determine what is stealing focus.
I think it's a Rewired issue, I had the impression it was something we noticed appearing after we started using it, but I've always thought it was an issue with our setup, so I never cared.
Of course this is a guess, all of our controls are written based on Rewired, a bit of a momentary lapse in knowing where to take your hands off, and I look forward to your discoveries.