Here is another scenario recently experienced in the field:
Cluster of gateways got upgraded to the R80.20.
Dedicated Gaia admin received version change notification and proceeded to snapshot the upgraded appliances.
Check Point admin, meanwhile, initiated policy installation.
Surprisingly, after about 40 minutes, both, the policy installation and the snapshots were completed, but there was an undeniable feeling of suspense and heavy perspiration while systems were solidly locked out with no option to cancel either process.
I guess what I am driving at is that there is supposed to be a communication channel between Gaia and SmartConsole or SmartServer that should prevent this kind of situations from happening by either refusing installation of the policy on the gateway with snapshot in progress and refusing to initiate snapshot until policy installation is completed.