[SOLVED] Dimmer Item behaving differently with simple Switch since upgrade to 2.4

I’ve just upgraded from 2.3 to running openHAB 2.4.0 Release Build via OpenHabian on a RPi3, and since the upgrade completed I’m having some problems with my Z-Wave lightbulb (DTA19 Smart LED Light).

The item is defined as:

Dimmer Light_Landing    "Dining Room Light"     <light>    (gDashboard) [Lighting]   {autoupdate="false", channel="zwave:device:f5fcc3ad:node4:switch_dimmer"}

Although it’s a dimmer, I usually have it set to either OFF or 100%, and I control this with a simple Switch in the sitemap:

Switch item=Light_Landing label="Dining Room"

Before upgrading - this was working perfectly but now it’s giving some strange behaviour. Trying to turn the light off no longer sets the dimming to zero, but to 49%. From the logs:

2019-11-24 17:17:38.612 [ome.event.ItemCommandEvent] - Item 'Light_Landing' received command OFF
2019-11-24 17:17:40.188 [vent.ItemStateChangedEvent] - Light_Landing changed from 100 to 49

This immediately turns the Switch item back to On - although the light is dimmed. Turning the switch off a second time does turn the light off:

2019-11-24 17:20:31.363 [vent.ItemStateChangedEvent] - Light_Landing changed from 49 to 0

I’ve been through my rules multiple times and don’t see anything that accounts for this behaviour - has something changed with how Dimmer objects work in 2.4?

No, but the binding has changed. A Lot!
Next update to 2.5 in 3 weeks or so.

I think the cause-effect is the other way round.

That’s straightforward, although we can’t tell from here exactly what the binding does with that.

That’s come from the device. Maybe it ramps down, and this is a status from partway along.
This might have something to do with “Command Poll period”

Ah! That’s exactly what it was - I’ve upped this value to 3000 and it’s working perfectly now.

Many thanks