Comments not showing anymore

Hi there, I set up a little site with wordpress and the “Mantra” theme.
Everything worked fine tho for some days comments don t show up anymore nor the “post comment Icons”
On my start page there s articles and everything worked fine. Tho on pages where I post galleries and such the commennt function is not working.
I checked individual page Setting (Show comments is “on”)
I checked discussion Settings, everything is fine there.
I tried using another theme, comments do show up there !
When I Switch back to Mantra they disappear.
When I Change the site Settings from Standard layout to “one column no siderbar” on certain pages it works again.
Any hint on my issue ?

Thank you,
Sebastian