Reading this thread I have found out that:
"PyQt GUI calls like setText() on a QLineEdit are not allowed from a thread. Anything that has PyQt painting outside of the main thread will not work."
setText() here is only one example, however, I believe there are more, I am just not sure how many and what. Could anyone provide me with a list of all the GUI calls that would require to not be ran from a thread, or explain me, how I could possibly find that myself? Thank you.