Issue might be a "simple" as VLAN A has lots of microbursts hitting its interfaces (BTW, if all the interfaces, in just one VLAN, are having this issue concurrently, possibly some form of broadcast storm).
Catalyst 3K and 2K switches are a bit "infamous" having smallish buffer resources (worst on the 2K) compounded by default QoS buffer allocations (believe your 3650 has QoS on by default, and 2K QoS off by default).
"Tweaking" buffer allocations can sometimes provide a huge improvement (i.e. decrease in discards).
In your issue is related to some form of broadcast storm, you might "analyze" traffic on that VLAN (e.g. WireShark) and/or try a couple of storm control settings (to see if that decreases output discards). (If you find, in fact, you have broadcast storms, than you can work to identify the cause and work or its elimination or mitigation.)