Delay when pressing multiple keys

Hello everyone!

Previously, I used Pianoteq with Roland FP 90 and Arturia. The combination was great with these pianos.

But now I've started using Casio GP 510 and I have one problem that I can't solve.

When 6 or more keys are pressed at the same time, a delay occurs. Some keys are pressed with a delay and not simultaneously.

Is there any way to solve this problem?

Thanks!