Cambium PMP450i Ethernet droppes while using a UPS

Does anyone know why using a UPS to keep equipment up during a power dip only the Cambium PMP450i has a LOT of port drops. Bypassing the ups the issue is no more.
Onsite there is a Radwin D+ port one on Mikrotik 2011 Cambium PMP540i port 2 Ubiquity AC port 4 and a Wavion Hotspot on port 3.
Only the Cambium gets dropped the whole time.
Removing the UPS and directly on AC the problem is no more