Transmit Discards across network and printers and MAC loses network connection

We have been experiencing a very frustrating issue where huge Tx Discards are seen on various ports on various switches across the network. Not always the same ports, not the same time of the day, and not every day. Recently though it has been every day. This is coupled with high utilization on those same interfaces 50% up to 80% and even over 100% utilization. When this happens, all the printers across the network lose network connection as well as the single Apple Mac we have in the organisation. The Windows workstations and servers don't seem to be affected.

I am desperate for an answer here as this is baffling even some senior network engineers I have spoken to.

Our current plan of action is as follows:

1. Buy a new switch and swap it out with the existing edge switches one by one to see if it is maybe a switch causing this.
2. Update all firmware on all switches
3. Use Wireshark to capture traffic before and during spikes
4. Create separate VLANs for printers
5. Switch off IPV6 for all devices on LAN (saw a reference to MLD packets causing a similar thing)
6. Last resort - update all network card drivers across the network (300 workstations!!!) - verylabor intensive....

Any advice is highly appreciated.