Bug WP latest version and NextGen

Hi,
as I upgraded to the latest version of WP and NextGen I noticed almost everyone is having problems with the galleries. I installed an older version of NextGen but still doesn’t work so I was wondering if it’s possible to return to an older version of WP.

if this is not possible what gallery viewer could I install to replace next gen? Would I have to work on all my galleries or is there a faster way to update the entire site?
Tanks