My kids relied heavily on their training wheels. I kept resetting them to see if the kids would balance more but they didn't. They just kept leaning to one side or the other. Finally I took them to our sloped driveway and got them to coast a little and head straight for the lawn. I told them crashing in the thick grass wouldn't hurt them but they should pedal as hard as they could when they hit it. Twenty minutes later we were riding on the street together and boy were they excited.
Maybe you can try it.