This is a mistake that many new proxy players often make, but now even experienced people have to be more careful. IP leaks (via DNS, WebRTC or simply proxy fingerprinting) are the number 1 reason why Facebook flags abnormally and locks accounts in a flash. Especially for BMs or accounts tagged as high risk, just one IP/location mismatch is enough to ruin it.
Don't trust the "safe residential proxy" advertisements - whether it's a 4G, mobile or DC cloaked proxy, you still need to test for leaks, check fingerprints carefully through tools like browserleaks, whoer, or set up a virtual machine to check behavior. Don't save a few bucks and lose a valuable account. If anyone has a list of fully tested proxy passes or an effective leak-avoidance setup, sharing is very valuable at this time. The game is more strict now.