I'll second the advice.
We're running Master and Local (rather than VRRP) but but connect to the Nextus 7K fabric.
With Spanning-Tree off on each vlan (missed the global trick) we were great until we added a VLAN and forgot to turn it off there.
Fortunately the STP block wasn't catastrophic and we were able to recover smoothly.
We now also turn it off globally.