Mancraft in G36 feed issues

[Szelwa]

Hi all. 
I hope someone will be able to share some ideas how to fix my problem. 
I just finished fitting mancraft v3 into the Specna Arms G36 (same as ares). Took me some time with dremel to make it fit into gearbox as original mancraft v3 gearbox would not fit at all in the gun. 
Trouble I have is that rif is feeding 2 bbs at the time. I adjusted and tested length of the original nozzle than swap for the 24.5mm one dedicated for G36 for better air seal. 
Swapped hop up as well as tested 2 different mags hi cap and low cap TM. 
To no change. 
Worth to mention I had same problem on this one while it was aeg.