I'm are currently running into the issue that when I navigate to a page which uses a full-bleed web part and put it in edit mode, it will show blank web parts.
It's a bit hard to explain, but here you can see what is happening (using a custom web part):

I'm also able to reproduce it by using only first web parts (hero web part + snippet web part):

When opening the developer console, I see the following error:

When removing the full-width zone and web part, it doesn't give this issue.
These are the steps to reproduce it:
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Adding to this thread a version using 100% OOTB components.

Thanks!
We think we know where the problem is and we believe we just released a fix that address the issue.
@estruyf (Elio), can you please check and let us know if the problem still occurs?
Thanks a lot
Still seems to occur.

Edit: This was related to another issue, was mixing up things
k, thanks @estruyf . Mind sharing tenant information? you can do that in the private channel if you want.
Same problem here, in IE, Edge and Chrome.
@lucabandMSFT this issue seems to be solved. I'm unable to reproduce it.
@MRuimerman do you still experience it?
@estruyf Yes, it is fixed in the default SharePoint webparts.
(Not in our own custom webparts but that is probably our problem.)
@estruyf , you guys ok to close this one? also, to be clear, you said that this is a different issue of #3856 , yes?
This issue is about the blank web parts when having a full-width zone and that seems to be fixed. So it can be closed.
Issue #3856 is about some styling which automatically gets applied to web parts in a full width zone. That's not solved yet. I mixed both before, as I was checking the status and replied in the wrong issue.
perfect. closing it. thanks a lot.
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Adding to this thread a version using 100% OOTB components.
Thanks!