So, the bottom left flipper sticks in the up position. It remains stuck after powering off.

Usually, to get it to release, I power off the machine, remove the glass, and manually flip it back to the down position. When doing this, there is a bit of resistance - the plunger is stuck in the solenoid and it doesn't want to let go.

The solenoid appears to be pretty new (bought the machine a month ago, solenoid looks like it is a year old).

I've spent some time searching old threads this morning and don't see a fix for what appears to be a mechanical problem. The fact that the issue persists after powering off indicates to this novice it isn't an electronic issue (fliptronic board, diodes, etc) but IDK.

What would the most likely cause be? Wondering where to start.

Thanks for the replies guys. I should have added - it looks like the flipper was rebuilt when the coil was replaced (about a year ago). The assembly is pretty shiny and new looking.

I do have a spare coil sleeve... Guess I'll disassemble the flipper assembly and see what it looks like. I tried lubricating everything yesterday and it didn't help.

This could be it. I noticed the newer coils are 11629s instead of the original 15411s. It's possible the extra kick is exacerbating the problem you mentioned. I'll check it out...

A little follow up. Thanks to everyone for the ideas - these are all worth trying even if it hasn't fixed the issue.

Swapped out the coil sleeve. Adjusted the spacing between the flipper bat and bushing and checked alignment. The coil stop and plunger look brand new - clearly rebuilt recently. Same problem.

The pictures in Vids guide are super helpful BTW. https://pinside.com/pinball/forum/topic/vids-guide-to-upgradingrebuilding-flippers

I'm stumped. Ordering a flipper rebuild kit today to replace what is clearly a recently rebuilt flipper.

Figured I'd get started disassembling the flipper in advance of receiving the rebuild kit.

Looks like I found the problem. http://i.imgur.com/hXiU5ro.jpg

The damage was concealed by the metal bracket holding this in place. The broken piece on the flipper link is plastic. Its likely the stronger coil mentioned above was strong enough to break it. Guess I'll keep a few spares. If it happens again, I suppose I'll replace the coil with the factory 15411.

Thanks again everyone. I'm posting this resolution in case it helps someone else down the road.