If it stays up with the power off it's not a diode. What parts weren't replaced when you did the rebuild?

The paper is likely to wear out and you'll be back to the drawing board. What I've seen make these style flipper stick is worn sleeves (the split ones that go around the plungers and rest in the "L bracket"), that same "L bracket" being not quite at a 90 degree bend where it mounts to the plate, this is critical (actually so are good sleeves). Gap not correct between the flipper bat and playfield bushing, too low or too high, puts the plunger in a bind. If you got a rebuild kit use everything. This old bally flippers are tricky and getting everything adjusted right is crucial for them to act right.

Linear flippers suck. Get a conversion kit to make them like the previous style, rotational flipper. You do all that work to get the flips Just Right, then the metal and Teflon bang around a little and you're back to sticky-icky.

http://www.pbresource.com/rebuildkit.html#KT-BFLIP03

Not sure if you can re-use the baseplate. If you can, spin it around so all your screw holes will be fresh.

Just as another view, I did Vids recommended change from linear to http://www.pbresource.com/rebuildkit.html#KT-BFLIP03
and I really wasn't very happy. I find a fast, or even medium speed ball, will push the flippers down if they are in an up position when hit; which didn't happen before. Myslef and a few other people have been asking to see if we did something wrong and never got a resolution so maybe you have to choose from one or the other problem?

They shouldn't collapse. With all the tungsten points filed (or new) and everything adjusted just so, they should be very snappy and impervious to ball collapse.

Yep, that's what we've heard but no dice yet. Brand new flipper rebuild kits listed above.

I have fixed this problem 100s of times and it is not always the same problem causing it.All of the above and
another thing i discovered quite recently is that sometimes the bracket that holds the coil gets out of round, letting the coil move a bit causing the hangup, especially when a brass sleeve is used at some time. It is a part that is not in the service kits, so mostly overlooked. Took me some time (30?years) to find this one out.
I don't like changing parts to the older flippers, especially in home use since the game plays different. Flash Gordon gets that special feel for the gameplay with the linear flippers that i remember so well when it was new. The older flippers are more snappier because the parts are lighter.

Yep, although I was too young to remember it new... Ahem, I do like the feel of the linears. I like the feel of most flipper types. Each one is special to each manufacturer and time period. These linears just feel right at home in the old Bally's.

+1. I would suspect this is what is going on if paper between the plunger and coil stop helped. I have seen this many times. Replace the coil stops.

He said he bought a rebuild kit and rebuilt the flippers and that should have included new coil stops. If it did perhaps the bat is too tight to the playfield bushing with no up and down play?

It still could just be re-magnetizing the new coil stops. A different brand may need to be used. I know this is generally frowned on, but tightening the spring ever so slightly may be enough to resolve the issue, as well. If it's the assembly is not out of alignment and not over-plunging to the point of getting stuck, then this is a possible cause.

I'll bet your sticking problem is with the coil stops in the linear kit, I ran into that issue a number of years ago and changed the stops--problem went away.

As far as those linear flipper go, be sure to cut your return spring in half if you want a better flipper return. Bally issued a service bulletin some time after the linear flippers went into service to address customer and operator complaints. Their advice was to cut the spring in half to improve the flipper return. Hard to say if flippers on your particular game have the correct return spring.

As a player and operator, I am not a fan of the linear flipper design, but hey if you like it then it is your game do what you want. OTOH, those linear slingshot kickers are much worse than the previous design and were a complete cluster, can't stand those assemblies.