I have closed the topic, as
I am unsure whether there is an actual issue or if I made an error during data collection.
There were numerous subscription bookings from a single user with implausible entries, which raised my suspicion that something worth investigating might be happening.
However, after restarting the browser,
I could not reproduce the effect. And without concrete, verifiable data, I have decided to classify the issue under "strange effects."
Thank you for your input on potential causes, though.