DUALR3 (non-Lite) – shutter moves on its own with long cable run. Need tips to stop “ghost” commands

Ideas & Suggestion
1

Hi everyone!

I’m trying to tame a rather stubborn setup and would love some feedback.

Hardware

  • Controller: Sonoff DUALR3 (full version, not Lite) – firmware 1.6.1

  • Mode: Motor (Shutter) – calibrated, works fine via app

  • Motor: 230 V tubular shutter motor (standard up/down leads)

  • Wiring:
    • Push-buttons → S1/S2 → about 7 m of in-wall cable → DUALR3
    • DUALR3 → motor (L-Up / L-Down), about 10 cm cable

Issue
After a random amount of time (seconds to hours) the shutter rolls up or down all by itself. Logs in eWeLink app show real “button” events, so S1/S2 are definitely seeing a pulse.

I have tried:

  • Swapped this DUALR3 with another from a different room → the problem stays in this location, so the issue is the line, not the device.

Sonoff support also confirmed the DUALR3 does not have galvanic isolation on the S1/S2 inputs, so a long cable can act like an antenna or somehow create interferences that signal S1/S2. The manufacturer requires an isolated relay for this motor – my mistake for not checking earlier.

Questions for the community

  1. Has anyone successfully run S1/S2 over more than 5 m without false triggers? Any shielding or ferrite tips?
  2. Is there a hidden parameter (Tasmota style) to extend debounce?
  3. If I keep the DUALR3:
  • Would an opto-isolated interface module between S1/S2 and the wall switch solve it?
  • Any recommended EMI filters or MOVs you’ve used with shutter motors?
  1. If I replace the DUALR3 for this location, which Sonoff, Shelly, or Finder module with dry-contact relays would you recommend for a 230 V shutter? (Power and energy metering would be a plus but not relevant for me)

I can post pictures of the PCB and wiring if that helps.
Big thanks in advance – any trick or pointer is welcome!