check cables lengths and integrity. also 100BaseTX/FX reported by sh int seems strange for me. is it a "twin port" where only one physical connector is active in any time? try to hardcode media for this int in that case.
Half duplex is perfectly fine on a link where you are not expecting a lot of raw-throughput. The only time you will notice a performance difference is if you intend to do 80% or more bandwitdh (in 100mbps that is 8 Megabytes per second) each way simultaneously. you can do one way at 8, or two ways at 4. (Very roughly speaking).
For obvious reasons, full-duplex will give you up to 2x the bandwidth available because the bidirectional traffic is not sharing the bandwidth.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...