BUG : Background image not visible on tactics or analysis board

Like I have written in the title the background image (transparent mode) cant be displayed on the tactics site (normal / streak) as well as on the analysis boards. I dont know it this occurs often but here is the picture i used:



That Bug doesnt happen with the picture lichess give us, but with external links.
Hope it's easy to fix.

Thanks in advance
Dolg

I forgot to add I use firefox (88.0.1) but the same problems occur on chrome (Version 91.0.4472.77), too.

See this issue :

github.com/ornicar/lila/issues/6684