Ring Intercom with Urmet 1131/002G - Audio In issues

Hi, I just received and installed the new Ring Intercom on an Urmet 1131-002G but I have an issue that sometimes I can’t hear the caller but the caller will always hear me correctly. I can’t pin down when or why this happens, it seems random, sometimes I can hear the caller without a problem and other times it’s just blank. I’ve rewired everything and made sure it’s wired correctly, also reset the intercom multiple times but nothing seems to fix it.