Hm, thanks for sharing. I had no test, but in my experiences modal forms give no control to AutoCAD for picking points or entities after dcl-form-hide. You have to dcl-form-close before and reopen the form by dcl-form-show again. dcl-form-hide my work with modeless forms, but, as I said, I have no experiencee with that workflow.
Regards, Fred Tomke