Clearly the drainage has been compromised. Has the tree ever been root pruned and repotted? If not, you need to do so and soon. While this is not an ideal time for this activity, waiting until a more suitable time will seriously jeopardize the health of your tree, if it has not been done already. Poor drainage is typically the kiss of death for Japanese maples. It also sounds as if the tree is seriously rootbound in the container, which is also a very stressful situation - containerized plants that become seriously rootbound are unable to access needed nutrients (you'll find most of the soil/potting mix has disappeared) or moisture (if not in the compromised drainage state yours seems to be in) and growth will be stunted. Stressed plants are much more prone to insect and disease problems as well.

I'd recommend removing the tree from the container immediately, root prune as necessary and repot with fresh potting soil. It is also possible you will need to bump up the container size although careful root pruning may avoid this need. You should allow at least a 2" clearance from the root mass to the sides of the container.

Thank you. sounds like my best way to proceed would be to plant it in the ground somewhere in my landscape. I can always use the container for something else. it is pretty small. It is 16 inches square and about the same height. I bet the plant now has nowhere to go with its roots.