Solarwinds shows our core and the switch our hyperconverged system plugs into reports a lot of errors and discards.

Solarwinds shows our core and the switch our hyperconverged system plugs into reports a lot of errors and discards (billions). We have a stack of 4 C3750s (our core layer 3) and a 3850 10GB switch.  We have a hyper-converged (HPE OmniStack) system that is plugged into the 10GB switch.  We don't have any routing setup. The port that was selected to be the blocked port for spanning-tree has been the one selected since the system was installed 15 yrs ago.  We have added about 12 switches, maybe more.  Maybe we need routing and an new port to block spanning tree.  I am not familiar with this level of network troubleshooting I am semi-new to networking, and have been promoted to Network Administrator about three years ago because there wasn't a position, and I have a CCNA, but I don't think that is going to help me troubleshoot this.  I'm not sure what to check.  Unfortunately, this is a manufacturing facility with PLCs that do a lot of multicasting .  The PLC environment is not really separated from the regular network.  It is isolated by a VLAN. We have about 20 VLANS.  I believe the system has out grown itself.  Is there a place I can begin to troubleshoot what we currently have?