Hello Roger. I was working with Apple technical support and it looks like at this point Apple is aware of the issue. Hopefully we see a fix in the near future, probably in the form of a GarageBand or iOS update. I'm not really sure.
I was able to test both on two other devices, iPad Pro and iPhone 5S. The iPad Pro running iOS 10.3 had the same delay problem. The iPhone 5S running the previous version of iOS just before the 10.3 update had no issues, no delay.
Apple suggested trying the 10.3.1 update but stated that they did not think it would help. They were correct. Same delay.