Did you check the coil stop, too?

If you lift the playfield and move the flipper with your finger, can you replicate the issue?

Usually when I see this the coil stop has come loose (a problem on Batman and Iron Maiden for me), flipper spring detached, plunger mushroomed (older games), etc. You might also check all the screws in the flipper base. Sometimes these come loose (especially with shaker motors installed). There are 8 around the base (two in each corner). A cracked bushing can also cause this. If you grab the flipper above the base and try to wobble it back and forth. Also if there is too much play (up and down lifting the flipper bay) that can cause it (I have had JJP come from the factory with too much play and had that problem). I agree, that try to replicate the problem manually with game off. You can also check if it is getting hung up on EOS, which sometimes bends. Once I take it apart, I generally replace the flipper sleeve as this is a cheap part. Finally the screw between the pawl and link arm can also wear out and cause the problem.

As you can tell by the excellent quality of the replies to your post, flipper problems are common!

I suppose it could be electrical, with the computer holding the flipper up because of the flipper button switch... but that would really be an unusual problem.

Take the glass off your machine, start a game, when the flipper bat is not coming down, is the coil engaged?, or is the flipper bat just stuck upward? You'll be able to tell instantly if you just grab the flipper bat and feel what it's doing.

Let us know what you find. There are at least seven different mechanical problems that can cause this, and all have been mentioned above.

check the up/down play of the flipper bat and linkage. should be able to wiggle up down about 1/16-1/8"