Brand new Devo 6s ... almost no range :'-(

I was so happy I had found a Devo 6s, at a clearance sale.
When it arrived, I switched the internals to mode 2 (and doing so I broke the guarantee seal). I installed Vlad_vy's build with Deviation 5.0.0 files. I easily bound my 2 multicopters with DSMX protocol.
But when I went to the flying field last day, both of them would lose signal as little as 10m away on 150mw tx power
At home, I re-bound the receivers with my trusty range-modded 7e, with DSM2 protocol (it ran a 4.0.1 nightly build which didn't seem to run dsmx protocol correctly) and I had a solid signal on low power settings.
I also tried binding a Devo RX601 with the 6s, but that too had poor range.
So I'm thinking the Devo-S-module of my 6s is actually faulty... Or am I missing something ?

I forgot to mention it, but I checked that too. The connector is correctly clicked in.

www.banggood.com/CC2500-NRF24L01-A7105-C...07.html?rmmds=search

I Would go this route....

with this antenna

www.banggood.com/Wholesale-FrSky-Receive...00.html?rmmds=search

Thanks !
Actually that's what I did after I posted this topic. The module has arrived and is installed, and everything seems OK now. I get ~9m range inside the house on 100µW with DSMX sats.