I found another thread talking about similar thing Switching automatically to preferred RAT - #4 by Linkin-Q
The answer is related to a documentation Quectel_BG95BG77BG600L_Series_Network_Searching_Scheme_Introduction_V2.0 §8 question 2. I don’t know if it’s the documentation talked by tabor.tang-Q.
I’ve tried it, I could say that registering to a network take more time when cleaning the frequency history first ([5;20] seconds to [50;80] seconds).
Since I don’t have a product which is stuck in GSM, I cannot test it under these conditions.