As I didn't get any response on my email in 6 days, let me post the issue in brief. I just want to be sure the issue is well understood, so the team can improve their product.
Test done via the Android app (on a Samsung Galaxy A70). Paying subscriber.
Save the page in Raindrop after making some highlights in the first parts immediately after saving.
Now wait until the flat, stripped-down version of the page appears when you open it in Raindrop (this takes over a minute on my smartphone). An enormous chunk at the beginning of the article has disappeared - including the highlighted parts in it. The first three highlighted phrases are still (partially) available under the highlights section, but its context has vanished, so even those have become almost worthless. In the web browser (e.g. chrome) the article may appear correctly though (but this was not always the case in my many tests)
It seems to me that this is an app design problem. There is some activity that is being done "in the cloud" and with some delay. This is probably done in order to avoid the situation that the user has to wait 1 or 2 minutes before he can start highlighting the text that he just saved with the purpose of highlighting. This is great. But this implementation now seems to come at a cost of unpredictability.