Can't write to a custom Characteristic through EspruinoHub (stuck at "Getting Service")

Thanks for the tips. Finally figured it out – turning off the WiFi module of the Raspberry Pi (putting dtoverlay=pi3-disable-wifi into /boot/config.txt) has helped big time, basically resolved the issue. I saw the advice somewhere else before, not sure where, but tried it only now.

Now it works nicely most of the time. It just occasionally times out with:

<Connect> de:vi:ce:ad:dr: Getting Service...
<Connect> de:vi:ce:ad:dr: Disconnecting due to lack of use (after 10 secs)
<Connect> de:vi:ce:ad:dr: Disconnecting.

Is this expected? Do you see the same behaviour? Any ideas how to achieve more reliability, apart from maintaining a persistent connection?