American Standard flush problems

We installed an American Standard Glenwall toilet with a sloan flush valve tank and it takes two flushes to get it clean. This toilet took the place of an Eljer wall mount with a cracked tank. We have tried adjustment of the tank and clearing the line and still needs two flushes.
Any ideas as to what else could be wrong, or have you heard of problems with these models.

flush

Those units rely on a trapped air bubble to supply the flushing force. If it loses the bubble it will only flush as long as the handle is depressed. If it loses part of the bubble it will only give a partial flush. Drain ALL the water out of the unit, see the instructions, and that will restore the bubble.

The Glenwall will almost never plug.
However, the high speed jet can shred paper.
It can sometimes need two flushes to completely remove the small particles.