I actually had a similar problem with the 4D menu: I found that TouchLock is disabled after invoking the assistant (Siri, in my case.) I reported the issue to support some time ago and would expect it to be fixed with Bragi OS 3.1.
However, just yesterday I noticed that TouchLock was disabled after making a phone call. I haven’t reported this to support yet, as I’m wondering if the fix for the assistant invocation will also fix the issue when making calls.
I’ll try to remember to post an update here when 3.1 is released.