I'm coming across a similar issue, I am able to open the page I want, edit text, move images around, however when I go to click +Image, the Gridder just disappears completely.
I tried the solution suggested here, but it hasn't worked.
I did all restart browser, cleared caches, other bug fixes that have been recommended in general, etc.
All the plug-ins are updated.
There aren't other plug-ins that are enabled.
Not sure if it's related but I'm unable to view the Media Library either?
We haven't done anything 'experimental', there has been no issues the past few weeks we've been working on this until today. The website works perfectly on desktop and mobile so we're a bit hesitant to mess around too much!