Occasional scrambling of data on Bluetooth UART after automatic reconnects?

Thanks - that is really interesting and a very important insight that these chars actually have a meaning.

The webpage is a json string from my internal home automation system and contains <2000 ascii chars.

For better reproducibility and to check, whether the size plays a role, I'm now making a test with the "Hello World!" test server https://pur3.co.uk/hello.txt and I'll report whether the issue also occurs with this very short string.

I have already realized that it's a battery issue, my battery life is around 2 days with 1 request/sec. I'll leave it this way for stress testing, but you are right and I should decrease the rate in favor of battery life at some point...