Generally speaking, the map is a container full of img elements. each img element represents a tile. In other words, the images are requested by the browser - not by us and therefore we do not have access to that request and check whether it succeeded.
Nevertheless, you could add a service worker
to your page and use it as a proxy to check whether there is a failing request.
Also, I can suggest you to take a look at the following thread where testing whether images are loaded correctly is discussed:
I hope this helps
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