MINI-ZBDIM: constant ~1 s delay processing every command; wall switch press takes ~2 s (fw 1.0.5)

What happened?

The MINI-ZBDIM (fw 1.0.5, latest) reacts very slowly to everything, both on the wired switch and over Zigbee:

• Pressing the wired momentary switch (S1/S2, double pulse mode, factory default) takes over a second before the light starts to change, closer to 2 s in total. Feels like the firmware first waits out a ~1 s multi-press window before doing anything. Turning off seems to be much snappier. Same on all ~20 units I have installed behind momentary rocker switches.
• Any command or even a plain attribute read from Z2M takes a constant ~1 s from MQTT publish to the device response. Always the same time, no retry jitter, so it's not a link problem. The device is a Router one hop from the coordinator and the network is quiet.

Things I already tried / ruled out:

• transitionTime (cluster 0xFC11, attr 0x001F) is 0, confirmed by raw read (had to write it raw because of #30549).
• All transition times set to 0, min_brightness_threshold / max_brightness_threshold across their range, dimming_light_rate at max, different external_trigger_mode values - no difference at all.
• delayed_power_on off, dimming calibration done.
• Same behavior on every unit I have (~20 installed).

What did you expect to happen?

The switch to react within a few hundred ms, and commands/reads to be handled in tens of ms like other mains-powered devices.

How to reproduce it

1. Pair a MINI-ZBDIM on fw 1.0.5.
2. Publish {"state": ""} to zigbee2mqtt/<device>/get and time the response: ~1.07 s every time.
3. Press a momentary switch wired to S1/S2: the light reacts after ~1 s, ~2 s total.

Zigbee2MQTT version

2.13.0 (Home Assistant add-on)

Adapter firmware version

7.4.4 [GA] (EmberZNet, EZSP v13)

Adapter

SONOFF ZBDongle-E (V2, EFR32MG21), ember driver

Setup

Zigbee2MQTT Home Assistant add-on (zigbee2mqtt/hassio-zigbee2mqtt) on Home Assistant OS, x86-64 VM under Proxmox

Device database.db entry

{"id":2,"type":"Router","ieeeAddr":"0xb0e8e8fffef9872f","nwkAddr":13235,"manufId":4742,"manufName":"SONOFF","powerSource":"Mains (single phase)","modelId":"MINI-ZBDIM","epList":[1,242],"endpoints":{"1":{"profId":260,"epId":1,"devId":257,"inClusterList":[0,3,4,5,6,8,2820,2821,64599,64529],"outClusterList":[25],"clusters":{"genOnOff":{"attributes":{"onOff":0,"startUpOnOff":0}},"genLevelCtrl":{"attributes":{"currentLevel":0}},"genBasic":{"attributes":{"modelId":"MINI-ZBDIM","manufacturerName":"SONOFF","powerSource":1,"zclVersion":8,"appVersion":0,"stackVersion":0,"hwVersion":0,"dateCode":"20251205","swBuildId":"1.0.5"}},"haElectricalMeasurement":{"attributes":{"rmsVoltage":0,"rmsCurrent":0,"activePower":0}},"customClusterEwelink":{"attributes":{"17":"\u0004\u0005\u0005\u0010\u0001\u0001\u0002","33":0,"16388":0,"16389":0,"externalTriggerMode":3,"calibrationStatus":3,"minBrightnessThreshold":17,"maxBrightnessThreshold":181,"dimmingLightRate":4,"levelForCalibration":0,"networkLed":1,"transitionTime":0,"delayedPowerOnState":0,"acCurrentCurrentValue":0,"acCurrentVoltageValue":234100,"acCurrentPowerValue":80,"delayedPowerOnTime":86,"faultCode":84017152,"calibrationProgress":100,"setCalibrationAction":""}}},"binds":[{"cluster":6,"type":"endpoint","deviceIeeeAddress":"0xe0798dfffe8f80c9","endpointID":1},{"cluster":8,"type":"endpoint","deviceIeeeAddress":"0xe0798dfffe8f80c9","endpointID":1},{"cluster":64529,"type":"endpoint","deviceIeeeAddress":"0xe0798dfffe8f80c9","endpointID":1},{"cluster":2820,"type":"endpoint","deviceIeeeAddress":"0xe0798dfffe8f80c9","endpointID":1}],"configuredReportings":[{"cluster":6,"attrId":0,"minRepIntval":0,"maxRepIntval":65000,"repChange":1},{"cluster":8,"attrId":0,"minRepIntval":5,"maxRepIntval":65000,"repChange":1},{"cluster":2820,"attrId":1291,"minRepIntval":60,"maxRepIntval":3600,"repChange":10},{"cluster":2820,"attrId":1288,"minRepIntval":60,"maxRepIntval":3600,"repChange":10},{"cluster":2820,"attrId":1285,"minRepIntval":60,"maxRepIntval":3600,"repChange":10},{"cluster":64529,"attrId":28678,"minRepIntval":60,"maxRepIntval":3600,"repChange":0},{"cluster":64529,"attrId":28677,"minRepIntval":60,"maxRepIntval":3600,"repChange":0},{"cluster":64529,"attrId":28676,"minRepIntval":60,"maxRepIntval":3600,"repChange":0}],"meta":{}},"242":{"profId":41440,"epId":242,"devId":97,"inClusterList":[],"outClusterList":[33],"clusters":{},"binds":[],"configuredReportings":[],"meta":{}}},"appVersion":0,"stackVersion":0,"hwVersion":0,"dateCode":"20251205","swBuildId":"1.0.5","zclVersion":8,"interviewCompleted":true,"interviewState":"SUCCESSFUL","meta":{"configured":"0.0.0"},"lastSeen":1787577542392}

Notes

• This is most likely the device firmware, not Z2M - posting here because @CubeZ2mDeveloper handles MINI-ZBDIM issues in this repo (e.g. #32540) and 1.0.5 seems to be the only firmware ever released for it.
• ORB-ZBDIM (same platform) users report the same thing: "the physical device takes seconds to respond" (https://community.home-assistant.io/t/sonoff-orb-zbdim-zigbee-dimmer-wall-switch-with-z2m/986454).
• @CubeZ2mDeveloper: can this be fixed in a firmware update? Otherwise I am considering returning / selling everything. A ~2 s reaction on a physical wall switch makes the device really hard to live with. Happy to test a beta.

No repository file, test, or entry point is mentioned; the report points to MINI-ZBDIM firmware 1.0.5 and reproduces the delay through Zigbee2MQTT and a wired switch. Start by confirming the timing on the stated setup; done would require eliminating the roughly 1-second command/read delay and the roughly 2-second switch response.