I was doing an upgrade on our NETAPP filer from 7.3.6 to 8.1.4. We used the upgrade advisor and everything went fine on one node. I didn't see anywhere in the documentation to not failover until the code has been updated on both filers before doing a failover. I am now in a state where my secondary node is in takeover mode and updated all the firmware on the shelves/etc. If I try and fail back to the primary it gives many errors and dumps the core and reboots.
I'm not sure what to do at this point. I understand that I made a mistake at some point, but I would like to know next steps to see what I can do to recover this issue.