Overtemperature problem with Shelly Dimmer 2

In my living room I have 15 dimmerable led lights, divided in two zones:

zone A: 9 leds

zone B: 6 leds

They are actually controller by two relays: two finder 15.91.8.230.0000 (see image, with also electrical schema)

I recently bought two Shelly Dimmer 2 in order to replace my two relays and make my led lights smart.

I attached the two dimmers 2's using the first schema (with Neutral), which is essentially the same schema of the old finder relay (RP is now SW1, the strange symbol is now O).

At first glance, both shellys work.

However, the shelly which is connected to zone A (9 leds), after about 15 minutes of switch on at 100% (~70W consumption) shuts down with "overtemperature". It reports a temperature of roughly 105°C.

No problem with the shelly connected to zone B (6 leds, ~43W consumption). After some minutes, it reports a constant temperature of roughly 77°C.

This is a status captured roughly one minute before one of the shutdowns.

{"wifi_sta":{"connected":true,"ssid":"SigiNET","ip":"10.155.1.86","rssi":-27},"cloud":{"enabled":true,"connected":false},"mqtt":{"connected":false},"time":"00:08","unixtime":1617746930,"serial":89,"has_update":false,"mac":"E8DB84D6E30C","cfg_changed_cnt":2,"actions_stats":{"skipped":0},"lights":[{"ison":true,"source":"http","has_timer":false,"timer_started":0,"timer_duration":0,"timer_remaining":0,"mode":"white","brightness":100}],"meters":[{"power":67.91,"overpower":0.00,"is_valid":true, "timestamp":1617754130,"counters":[67.861, 67.939, 67.923],"total":2308}],"inputs":[{"input":0,"event":"","event_cnt":0},{"input":0,"event":"","event_cnt":0}],"tmp":{"tC":104.65,"tF":220.37, "is_valid":true},"calibrated":true,"calib_progress":0,"calib_status":0,"calib_running":0,"wire_mode":1,"forced_neutral":false,"overtemperature":false,"loaderror":0,"overpower":false,"debug":0,"update":{"status":"idle","has_update":false,"new_version":"20210323-110201/v1.10.1-gf276b51","old_version":"20210323-11020

I tried to swap the shellys (so I could exclude that one dimmer is defective), but behaviour is the same.

The one connected to zone A always goes to overtemperature after a while.

I tried to repeat calibration multiple times (also with "trailing edge") but with no avail.

Is there something I can do?

Should I return the shellys?

Hello,

in these days I tried everything.

I set Trailing edge. I repeated calibration a lot of times.

I downgraded firmware to 1.9.0. I upgraded to beta firmware 1.10.2.

But the result is always exactly the same.

After a while with lights on at 100%, the "shelly dimmer 2" with 9 leds (~70W load) becomes hotter and hotter, and when its temperature raises to ~105°C it switches off with overtemperature error.

First time it happens after about 10-15 minutes of activity. Then, if I switch it on again when it's still quite hot, it lasts less.

No problem with the other "dimmer 2" with 6 leds (~43W load): it becomes a bit hot (about 95°C) but then it keeps stable.

As stated before, I tried swapping them, so it's not a matter of a defective unit.

I don't understand why the shelly dimmers become so hot.

My previous simple shelly 1's never gave me problems.

If I keep open the electric box where the shellys are installed, the dimmer with 9 leds does not become so much hot, and it seems stable. However for obvious reasons I cannot keep it open.

I'm sad... If I don't find a solution soon, I think I'll have to return the shellies...