Are you sure the shutter speed isn't set for 60 seconds? In which case there is an S on top of the shutter speed. The pin to automatically switch from incident to reflected if not working correctly only gives you 2.7 stops error not as much as you say. The bias can be set on the meter but only 1 stop. Without having the meter in hand I must say thay your meter is in need of service. I can't think of user error that can cause that much of an error.
I am trying to think of all the user error possible.
1. the pin only gives you 2.7 stops off.
2. pointing the meter wrong way would give you lower reading and not higher reading.
3. Setting the meter adjustment only allowed for 1 stop.
4. Hemisphere getting old (I have this problem before) only gives you lower reading and generally less than 1 stop off.