We're having a similar problem, where 3 of the ports are configured to have the same baud rates and settings however, were experiencing faults on the 3rd port. There is a delay in bytes packets being transmitted out of the 3rd port. It only happens at every 11th byte being transmitted. The delay is small however high enough to be above the expected 9K6 baud. This is causing comms faults.
The below have been tried without any success,
1. setting the command #>set config optimize = latency
2. enabling "Complete Write Requests Immed” at the advanced properties
3. Compared all settings at web ui and advanced settings under windows device manager against port 1 and 2. (they are the same)
Is there anything else that can tried?