1.8.3 > 1.9 update triggered fatal PHP errors

After updating to 1.9 all my subsites (multisite) that had AIOEC active went offline with fatal PHP errors ??

The change log is blank for 1.9 so I’m nor sure if I was supposed to do something special for the update?

I rolled back to 1.8.3 and everything is working fine again.

Is 1.9 half baked or was it supposed to work? If so what the proper update procedure?

https://www.ads-software.com/extend/plugins/all-in-one-event-calendar/