Wings3D from FlatPak on postmarketOS - GUI menus behave weird

[idj]

Hello everyone.
I installed Wings3D on my SM-A500FU (Samsung Galaxy A5 - 2015), on postmarketOS (which is a Linux distro based on Alpine Linux, designed for phones) and it runs smoothly, but the menus are unusable.
Specifically, I can open the main menus (File, Edit, and so), but I can't select menu voices (in example, File -> Export, or File -> Save), because the focus gets redirected somewhere else (don't ask where, I don't know - xD).
I guess it's an issue strictly related to Wings3D, as every other package just works out of the box.

Thanks in advance for any help.

Regards.