The devices probably send the “ok I received your signal” too late, or homey processing them too late, or not receiving them at all.
If that is (too late) for 3 times it will sign the device as unreachable, or from 1 time of the “test” button. (this is only for mains powered devices)
Might be a range issue, or something else drastically lowering the range capabilities of those devices.
The basic on/off from the dev pages doesn’t wait for the ok signal back, only for if the zwave chip inside homey gives it the “signal send” state.
