Okay, finally got the original nrf24l01 SMD modules with the square chip visible... As exptected, things work just fine now, so the culprit of my issues was really the incompatible/fake "nrf24l01" SMD modules with the epoxy blob. If you want to use normal nrf24l01+ modules together with this smd gateway, DO
NOT USE the smd module with the epoxy blob, as they won't work.
Using only the fake SMD modules might work, too, but mixing the fake modules with real ones does not work.
@sentur since it was launched 6 days ago, I seriously doubt anyone has had the ability to try it.
Anyway, please don't post the same question in multiple places. It wastes people's time. Most users don't have as much time as they would like to spend on projects, and wasting their time by splitting the discussion to multiple threads isn't very nice.
In case anyone wants to follow the existing discussion, head over to https://forum.mysensors.org/post/84076
I faced similar issue and @TMRh20Projects replied in arduino forum. My issue was beacuse of cheap NRF modules chinese clones. After I replaced with good genuine ones, everything worked like a charm. Please check the NRF modules you are using. I wasted three days to figure out if there was some code issue, when at the end it was the NRF which created all the mess