Regression of the integrated preview window, which sometimes does not show parts of a web component

[Piiit]

Please compare the "Activity & POI" web component

https://webcomponents.opendatahub.bz.it/webcomponent/0e5fbede-4a21-4dd3-bf85-7d2be71dfb12
https://webcomponents.opendatahub.testingmachine.eu/webcomponent/0e5fbede-4a21-4dd3-bf85-7d2be71dfb12

Why is the same version working on the old store, but no longer on the new one?

UPDATE 2021-07-23

• We decided that this issue is non-blocking for the collaudo!
• We are at the moment out of ideas what could be the problem...
• Write to the original developers of the component to ask for help, maybe it is something inside that component itself
• we will have a look at it, if we find new inputs that could be tried
• The preview itself also does not work (not only in the iframe) see --> https://api.webcomponents.opendatahub.testingmachine.eu/preview/0e5fbede-4a21-4dd3-bf85-7d2be71dfb12/development-13-20210427T1906?attribs=PG9kaC1hY3Rpdml0eS1wb2kgbGF0PSI0Ni40OTgzIiBsb249IjExLjM1NDgiIHpvb209IjEwIiByYWRpdXM9IiIgbGFuZ3VhZ2U9ImVuIiBzaG93cmFkaXVzPSJmYWxzZSIgY2F0ZWdvcnktZmlsdGVyPSIiIGRpcmVjdGlvbnM%2BPC9vZGgtYWN0aXZpdHktcG9pPg%3D%3D

[SirCotare]

@Piiit interestingly it is working properly when I run it on localhost.
I have investigated a bit further and I have come up with a possible cause of the problem.
I compared the response headers and noticed that there are some differences between the live server and the test server.
Testserver sends:

X-Content-Type-Options: nosniff
X-XSS-Protection: 1; mode=block

Livesever does not.

As far as I know those headers could potentially cause trouble.
Can you check if removing those headers would resolve the issue? So at least we can verify if that is even the cause at all.

[Piiit]

@SirCotare Hi, I am unable to reproduce what you say on my localhost... it always does not show the icons and menu of the web component, also with those header fields disabled.

What I see thou is that the old CDN reported the correct svg mimetype, and the new cdn shows only javascript for that

[Piiit]

@SirCotare I thought it might be related to the mimetype. I fixed that now, but the problem remains... also on my local machine. What else could it be?

[Piiit]

Now, as I deleted the cache and reloaded the page several times on localhost, the icons show up... but not always. could it be a race-condition, or a surrounding div or css that causes those problems... maybe something that gets not loaded fast enough... still not sure where it comes from

[SirCotare]

Honestly, I'm pretty much out of ideas at this point. The preview is still wrapped in an iframe to prevent the store from causing trouble. All resources seem to load correctly. When I turn on 3G slow network simulation, it also works.
The only difference I see is, that you probably used the cli script to import the webcomponent while I used the crawler. That still does not explain why it works on your localhost (sometimes).
Could it be that the order in which resources are loaded is relevant and we have a difference here? Just fishing for ideas...