Double Cross Dipole antenna for 437 MHz don't tune

I’m building a Double Cross Dipole antenna for 437 MHz to be used with a SDR receiver for CW cubesat.
The idea is to follow this “classic” paper from Gerald Martes, KD6JDJ.
I tuned every single dipole (8 mm aluminium bar + ferrite + coax cable) using a nanoVNA with – i think – good result(eg. here the return loss of first dipole)

I use a coax cable to measure the SWR like this

and the coax length is taken from end of the shield (as in this images :))

but when I connect all the 4 dipole … craziest thing happened …and it seems to me that every dipole change the proper resonant frequency to a different one.

Is the problem in the cabling between all the dipole ? Or (as I suppose) I followed a wrong apporoach tuning separately every dipole and the proper way is to tune all the arms after connect them together?

Can someone give me some hints on how to proceed?

Tks a lot

Carlo, IU2KQB