Negative Faith Per Turn?

This is an odd bug a friend and I ran into during multiplayer. This occurred after a random reload during normal play. When we were brought back to the map after it reloaded, I noticed that I was only generating 1 faith per turn, when I should've been generating 2. I have a shrine in the city, and a wine tile being worked that provides +1 faith and +1 culture (Goddess of Festivals Pantheon). I decided to tell the city to stop working the wine tile, and it went to +0 faith. I thought that The shrine was bugged or something, but selling it resulted in -1 faith per turn. Anyone else run into this bug?

Gee, that's weird. I don't know what could have caused it.