Hi, Thanks ??
Concerning the problem, I’ve read on many forums that it’s caused most of the time by an incompatibility with a wordpress extension.
So I have tried to disable each one cheking after if the problem was still there and that’s how I found the extension not compatible with the nirvana theme.
In my case it was “Huge-IT video gallery” used to make a video gallery from Vimeo. I have replace it by another one (uTubeVideo Gallery) and now it all work great ??