Unable to render native controls

[SamGR_WCC]

Hi, 
We have been building on a Power Page for a few weeks now, however seemingly over the weekend the following amber warning has appeared in the design view of the page. 
- "Unable to render native controls"
This seems to appear every time you navigate to the Pages Section in the design view.
There is a Learn More option next to this but it just takes us to be Bing home page. How useful...

In the design view this does not seem to be causing any issues, however we cannot preview the site. The preview button rarely does anything, and if you navigate directly to the URL it will take an age and then throw a 504 Gateway Timeout. This is not much to go off. 
This does not seem to be an environment issue as other pages can be previewed in the environment.

I have tried clearing Cache, and adding metadata for any SubGrids I have included as CoPilots advice, however this does not seem to have solved our problem.

I was hoping someone knows what the problem is and how to deal with it. 
Thanks!

[JadyMulqueeney]

We are getting the same error this week too. In several different environments. "Unable to render native controls" Maybe it is a new bug in Power Pages Editor? 

[irenegunning]

I'm getting the same issue.

[SamGR_WCC · Accepted solution]

There was an update over the weekend. If I was to guess, something that was perfectly fine in the last version is suddenly not fine, but the error messages give no guidance as to what that is. 

Edit: Although, we have checked this morning and the warning/error message is no longer showing. We are still getting that 504 gateway error though. I'm now unsure if they were linked. 

Edit: We have been able to resolve this problem by restarting the site. The error message went away on its own as mentioned above. 
Restarting the site is via the admin centre : 
'Set Up' -> 'Site Details' -> 'Open Admin Center' -> 'Site Actions' -> 'Restart site'