Shelly 2.5 - calibration failed but debug log says it was successful?

Hello everyone,

I have a 3T35-10B roller shutter (https://www.3t-motors.de/3T-Motors-Roll…-10Nm-SW40.html) that I want to control with my Shelly 2.5.

I already have four Shellys in my house that I was able to successfully calibrate.

With this new one however, the calibration simply stops nearly at the end and my app/browser tells me it failed.

Here is what I have tried so far:

* set the Shelly to roller shutter mode

* set the working time to 120 seconds

* tried the app and different browsers

* reset the device

The roller shutter moves down entirely, moves up entirely, then moves to ~20% open and stops for a while, then

* either moves to ~50% open and stops

or

* just stops

and tells me the calibration failed.

Video on Streamable.com

In the

Firmware is 20210909-144331/v1.11.4-DNSfix-ge6b2f6d.

What can I do???

Ok so I've now wired my Shelly like this:

When I plug in the USB, I see no difference in having the yellow wire (GPIO0) grounded or not (e.g. flashing LED on the Shelly or similar).

I also tried switching RXD and TXD (RXD -> RXD, TXD -> TXD vs. RXD -> TXD, TXD -> RXD).

No Matter what I do, the Shelly does not seem to connect:

Is it broken?

I found some tips on GitHub and Stackoverflow, however none of them worked for me.

Using this guide (https://github.com/yaourdt/mgos-to-tasmota) I was able to successfully flash OTA; first Tasmota, then Tasmota Minimal and then again the recovery firmware (1.5.10).

Using this, I was able to do the calibration.

Thank you very much your crucial hint!