Originally Posted by big john

The "lock" thing is called chainsuck. The ring picks up the chain from the bottom and pulls it up to the frame. I always thought worn rings contributed to this, but yours is all new? When I have had the chain get pulled up like that it sometimes tweaks the derailleur or bends the chain.

On my Ultegra bike the shifting goes bad after this happens if the front derailleur gets moved or bent. The other bike has Chorus and everything tends to come loose on that bike, including the derailleur clamp and even the stop screws. It's been working ok for a while but that thing has been plagued with dropping the chain more than any bike I've had. I shortened the chain a few months ago after discovering the shop that put it on (when I bought the crankset) left it too long.

I also went over the adjustments again and I snug the derailleur clamp often. Just go through it. Check the derailleur position and stop screws again and good luck.