My wife's old VW Beetle had a similar problem years back.
Parked in the sloping driveway, the float in the carb did not shut off the fuel properly and a little would run into the manifold overnight. The fuel would find its way into the cylinder, past the rings and into the crankcase.
We only noticed this because the oil consumption stopped.
Instead of a can every second tankful, it stayed full.
One morning we had fluid lock and it wouldn't turn over.
We towed to the shop and they identified the problem.
We had been running the VW motor with two stroke mix in the crankcase instead of oil !
The oil was changed and the filter changed.
Then we ran the motor for 1000kms before changing oil again.
That motor ran beautifully for another 14 years...