If you take the top off of the tank you will see a lever about 12 inches long that the flush handle moves up and down. To this is attached one end of a small chain. The other end of the chain is attached to the actual flush valve (which might be a flapper or a plastic column. The chain is probably getting a little tangled so that it does not allow the flush valve to return all of the way back down. You can confirm this by waiting until it happens again, then remove the tank top and look before you jiggle the handle. You might be able to remedy this by moving the hook on the end of the chain that is getting tangled. However, I have had better luck by replacing the chain with a flexible, but durable cable. I happened to have some large o-rings, which I cut, then put a knot in each end (after installation). Nylon string might work, but be sure to fuse the ends with a match. If you want to try the o-ring idea, go to any automotive service shop and ask them for a large o-ring, about the size that are used on disc brake pistons. Good luck.
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If you take the top off of the tank you will see a lever about 12 inches long that the flush handle moves up and down. To this is attached one end of a small chain. The other end of the chain is attached to the actual flush valve (which might be a flapper or a plastic column. The chain is probably getting a little tangled so that it does not allow the flush valve to return all of the way back down. You can confirm this by waiting until it happens again, then remove the tank top and look before you jiggle the handle. You might be able to remedy this by moving the hook on the end of the chain that is getting tangled. However, I have had better luck by replacing the chain with a flexible, but durable cable. I happened to have some large o-rings, which I cut, then put a knot in each end (after installation). Nylon string might work, but be sure to fuse the ends with a match. If you want to try the o-ring idea, go to any automotive service shop and ask them for a large o-ring, about the size that are used on disc brake pistons. Good luck.