I’ve taken the tank lid off and can see what is happening. The arm lever is getting caught under the flapper when you flush the toilet. It doesn’t matter how short or long I make the chain, the arm drops under the flapper and gets stuck.
You can jiggle that handle and it normally fixes it, but it seem like there is an adjustment I should be able to make to keep it from happening. Adjusting the chain length doesn’t seem to help.