Block settings not being saved in database

Guys, need your help again!

I can't enable and disable blocks in my 4.7 and 5.x sites. Weight and placement settings also are not being saved. When I save the new block settings, it just says 'The block settings have been updated.' -- but actually the settings remain the same.

I don't know if this was caused by my upgrade from 4.6 to 4.7.

Thanks in advance!