Hoping someone can help me diagnose issue with my garage door.
The door is small (single garage), old school wood door so it is a bit heavy. It is run by an ancient chain drive opener and has worked fine until recently.
It uses extension springs, not a torsion spring

When opening or closing, the door hangs up and starts "hammering" very loudly and needs to be manually persuaded to operate.

I can't see where the rails are bent any more than they have been since we bought the house and the opener seems to be operating fine.

Wondering if there are some obvious things I should be checking?

If it’s belt drive might need to adjust tension on the belt..

Gears in the opener maybe worn out and cogs sliding over each other?

Used to have a spray can of lube just for the wheels.

Know a gentlemen who lost an index finger in a garage door years ago. Use caution.

Try soaking the springs and wheels with a garage door lube. If nothing springs could be on the way out. My torsion springs just snapped a couple weeks ago. It was hammering the day before but still functional. Next day the springs snapped. Not a cheap repair. My belt drive motor is 1.5 years old with an insulated steel garage door.
The tech was shocked my springs were from 2001

Remove the extra slack in the chain check/replace the drive gear if need, buy a new opener might be ready for a new one.

Disengage the door from the opener and manually open. That would tell you if its the door or opener. I have replaced the worm gears before and didn't seem to last very long after that.

Thanks everyone.
I believe it is gears in the opener but I've been so busy I haven't had a chance to take the cover off.
Door runs smoothly when disengaged