[stomachmonkey]

I'm not aware of anything in the safety parts of a garage door system that will prevent it from opening so the fact that it opens without issue is likely irrelevant.

I've had the same exact problem with one of my doors over the last week.

I believe what has happened is the wire coming out of one of the sensors is borked.

The problem started for me on our last recycling day. I noticed one of the bins was pushed against the sensor and crushing the wire that comes out of it.

When the door first stopped closing reliably I checked sensor alignment, greased the rails and checked for other obstructions/binding in the system all to no avail.

Remembering the wire being crushed I started fiddling with it and it seems to be the only consistent thing that gets the door to close.