Upfront Fixer not updating anymore

Hi,
i'm using Fixer theme on http://klusjesmanpijnacker.happycmpr.nl/
and i did get to update the menu, but all other changes after that don't get saved.

I've tried several times. But without further luck. I don't know what next step to take now.

Hope you can point me in the right direction.

Thanks.

Radomir