We have been using RCM3200 module in our product for 15 years.
Recently we received a batch of RCM3200 modules from Arrows, and they are having communication problem, many broken/missing packets according to Wireshark captures. The module is used "as is" without any modification, and the same firmware has been working flawlessly in the past 15 years.
Comparing them with old ones, I noticed:
This batch all have a white mark of T14 and T4? on the Rabbit micro and they uses AX88796A Ethernet controller (I used up my previous batch so I have no idea what my previous batch uses, but a test module from old days uses AX88796 instead of AX88796A)
Maybe a bad batch of RCM3200 somehow got shipped to your distributor?