Have the exact same issue using same code layout. Submitted a feedback report but have not heard anything about the issue. What I discovered debuggin this issues is for some reason on the frist button press the @State variables are not set by the button press. Somehow the system reads that true for presenting the sheet but at no time is that variable ever registering as true during debugging. The second variable being set and passed to the new View is also never registering as set.
If you continue to select the same button, the same behavior happens until you choose a second different button. When this happens then all the State variables are properly set and the Sheet appears correctly.
Strange Bug that needs to be fixed if Apple wants iOS 14 compatibility.
Dave