NC-21.0.5: Icons aren't shown

Hello,
NC is running on shared webspace server (Hosteurope) with https

Some icons aren’t shown on desktop, but functionality is given. Pls refer to right upper corner (red marked).

How to get those icons back?

Thx!
Bildschirmbereich

Really no hint about this issue?
:face_with_raised_eyebrow:

Additional hint:
in .htaccess there are some security settings.

If deactivating:

Header set Content-Security-Policy "default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval'; style-src 'self' 'unsafe-inline'; img-src 'self' data:;"

with a comment mark (#), icons in NC pdf viewer are shown.

NC installation is on same server in subfolder /nc/ so why are icons not shown?

Thx + regards