Hey sorry for the late feedback xD my phone just went bye-bye today ^^
To your question, the UMG is a user widget yes. I had also tried instead of calling the Udpate function to simply print a string, but with the same result. I am still of the opinion that all instructions end up in the stack and are only processed at the end. Changing the variables directly in the UMG didn’t help either 
I haven’t tried an interface yet but I’ll give it a try and get back to you thanks!