Are you sure this is specific to Canosa and not something that would happen to you with other games ?

As a game developer, I'm not even sure I have any control over that button, to be honest.

I was able to reproduce it once.

I think I saw the buttons appear briefly, then diseappear when the popup "Rate this BGA adaptation" appeared.
If that's true, this bug could in theory happen with any Alpha game, because this popup appears all the time, and very rarely with published games as well.

I tried to reproduce it with other games, but failed. Unfortunately, that does not prove it's not possible, because even with Canosa, I only saw it only once in multiple attempts.

I set this report as "confirmed" because I reproduced it, but there is nothing I can do about it. I searched in both the code and the documentation and also asked fellow developpers, I don't see any way I or any game developper could control the appearance of these buttons. They are displayed by BGA directly

I was able to reproduce this bug again. I confirm this is related to the "Rate this BGA adaptation" popup. The buttons disappeared when I clicked "Cancel" in this popup. And I can also tell that this is not specific to Google Chrome and can happen on Firefox as well.

I was also able to detect that the buttons were not hidden (behind another UI element), they were completely removed.

I have no control over this popup or over the "leave", "replay" and "rematch" buttons. Although I have yet to reproduce it with another game, I'm still confient that the bug is related to this popup and not to Canosa.

It turns ou this bug was both related to the "Rate this BGA adaptation" popup and specific to BGA. Many thanks to Een who found out what went wrong.

The bug is fixed, I just pushed a new version.

Specific to Canosa, not specific to BGA, of course. :)