I did a search on the whole site for 'receive discards' & found the following posts which might be helpful in your situation:
One reason for receive discards on a switch is mismatched VLANs.
We had this problem show up all of a sudden on a "tagged" or trunk
port between our switches.
Check the Configured VLANs on each switch port.
The port with the RX discards will be "missing" a VLAN
as compared to the other end of the trunk.
The switch just "discards" the packets arriving on the missing VLAN.
Once the VLANs were matched up, the discards stopped.
I checked all switches at the facility.
All switches have the same VTP domain.
All switches are client (except for the main MDF switch which is server)
All uplinks are set for trunk mode, dot1q encapsulation
All switches have records of the same VLANs in their list.
All uplink switch ports have the same active trunking VLANs