Big white background picture makes App Symbols disappear

[Support intro]

I uploaded a big picture with white background.
It seem that this white color or picture itself is spreading into the line with the App Symbols. I cannot see app Symbols anymore. But when I click there, I hit them.
When I remove the big white background from design setup, all works fine again.

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Nextcloud version: 25.01
Operating system and version: Ubuntu stable