DI2 connectivity issues

Hello,
I've just moved from Edge 830 to Edge 840 solar. I use the ew-wu111 DI2 connectivity. It worked perferctly on 830 but on 840 I works very unstable. I had a setting to change the screens with a left handle, not it's just unusable.

I saw someone experienced the same problem here (another post) but the discussion is locked.

I tried with keeping the the computer next to the transmitter but the effect is the same.

Any ideas how to fix it? Thanks a lot!