For 1.2.2 version
if you found after updating the admin, gets 500 try to refresh again that might be issue for cache in code 

For 1.1.6 version 
-> If you are updating the panel to version 1.1.6, for the first time maybe it would be issue to update, try to update the same version twice.
-> After Update, if you are using stripe payment gateway check webhook signature of stripe is filled in system settings, if not update it.