"Are you sure?" checkbox and text missing for deleting pictures

[JanGoofy]

The checkbox + text is missing in this theme, switching to modus theme and it is back without tweeking any other settings in piwigo.
Pressing ctrl-A to mark all text on webpage makes "are you sure?" visible, but still no checkbox.
Tried in both Edge and FireFox, at various windows sizes as well.

See atached screenshots.

Bootstrap darkroom version 15-b
Piwigo core 15.3.0
Danish language pack, but I doubt that has any effect :-)