Hello @ContrivedTea675 .
I am not sure if a changing ip can cause issues, as I do not know how MSFS handles communication. If I understood correctly, you suffer from MSFS disconnection issues while flying probably noticed by a red banner that tells you that there is an internet issue?
What is you available internet speed and I assume you do not have a data limit?
I don’t know how your countries internet provider handles it, but in my country, the assigned IP does not change often and when it does, it would do probably between 2-4 o’clock. In my experience, such events or other issues should be logged by your router. Checking the log should be easier and more accurate for diagnostics than waiting for the problem and seeing if the ip changed.