Smartthings turns one sonoff on off problem

Hello

I have some sonoffs here (S20, all on the same tasmota FW), but one of them behaves very strange.

Theye are all triggererd from my tablet through tasker -> shaptools -> smartthings.
But 1 of them goes on and then off, although it has to stay on.
I tried it straight from the ST. Same behaviour, on -> off

I then logged into the webinterface of this sonoff, pushed the on button in the webinterface, and it staid on.

So, it has to be something in ST. But what?
Why is this sent ; 09:23:11: debug sendCommand(Power:Off) to device at 192.168.2.30:80?

And how can I solve this?

This is my live logging;
09:23:12: trace daysOk = true
09:23:12: debug evt.name: off
09:23:11: trace Not sending alert, no preferences set
09:23:11: trace oncePerDayOk = true
09:23:11: debug HH autoExecute(), newMode: null
09:23:11: debug HH auto execute Bedlamp Uit Something Turns On or Off
09:23:11: trace daysOk = true
09:23:11: debug evt.name: on
09:23:11: debug sendCommand(Power:Off) to device at 192.168.2.30:80
09:23:11: debug OFF
09:23:11: info switch is ON
09:23:10: info HH execute(true, null, null), newMode: null
09:23:11: debug sendCommand(Power:On) to device at 192.168.2.30:80
09:23:11: debug ON
09:23:11: debug sendCommand(Power:On) to device at 192.168.2.30:80
09:23:11: debug ON

Another Sonoff (using same device handler) is giving this log;
10:12:19: info switch is ON
10:12:19: info switch is ON
10:12:18: info HH execute(true, null, null), newMode: null
10:12:18: debug sendCommand(Power:On) to device at 192.168.2.7:80
10:12:18: debug ON