Shelly 1L without neutral with 2 way switches - works but first toggle not every time

I have connected 2 way switches and a Shelly 1L based on the discussion in this thread, finally settling with the following wiring on the right (proposed in the thread).

I don't have smart bulbs so both switches are in toggle mode. The shelly works perfectly through the app and the switches also work 90% of the time but not in two cases:

1. I turn the lamps on with Switch1 then I can turn on/off with Switch1 but when I want to turn off with Switch2 the first toggle doesn't do anything. By the second toggle it turns off and while using Switch2 works perfectly.

2. I turn the lamps off with Switch2 and then try to turn them on with Switch1 the first toggle doesn't do anything but the next and following toggles work as expected

All other scenarios works fine.

I hope I was able to describe the problem clearly.

Thanks for your help!

Yes, both buttons are set to toggle mode.

And yes, the live is connected to O and the bulbs are connected to the L pin. I also tried the other way around but then the Shelly was just turning on/off the relay continuously (maybe that's the flickering).

Thanks! I've just configured/tried and works perfectly. Thank you!