Hello again,
I am sorry that I haven't come back to you before.
Now, a year later, I have conducted the same test again on a new phone and on Android 11 and the Map component still shows the same behaviour.
The responses are HTTP 200s with payloads.
Actually, I may refer you to another thread where a developer has also experienced the issue: Unpredictable data usage Map
Is this app-private cache directory supposed to be found in the Internal Storage at Android/data/appinventor.ai_user.appname/cache ? If this is the case, I cannot find it.
EDIT: After some more digging, I found that my test app created this directory (osmdroid/tiles) in the Internal Storage after being granted Storage permission (i.e. NOT at Android/data/etc but at the Internal Storage's (aka SD card) top level)! But from what I can tell, it remains empty and the issue persists. But the map component does have some kind of working cache (maybe at /data/data/app/cache? I cannot verify that, my device isn't rooted).
My suspicion is that osmdroid may be badly configured.
I made a screen recording of the app while it is trying to display affected tiles: Google Drive link. You can clearly see something flickering on the map. What's strange is that it seems to load two different versions of one tile. I made sure to clear the app's cache previously so that it should load all tiles freshly.
Leo