Hi Jim,
I followed exactly your steps to repro the issue using the latest Quet Web Parts 5.4 (recently released) and I couldn't.
On the screenshot below the field Weight is the type of Number and as soon as you leave the form a validation occurs. If the validation fails the forms events Save and PostBack are cancelled.
Hitting Save won't do anything as well as changing the Language field that has Auto PostBack enabled.
What is the version of the QWP are you using?
Thanks,
