No signal on 2nd SDI out

Hello everyone,
Our setup is the following :
Videohub 40x40 and 56 TVs.
The 40 TVs that are connected to the Micro Converters HDMI to SDI 3G on the first sdi out port work great.
The extra 16 TVs that are connected on the 2nd sdi out port of the converters , randomly loose signal.
The hdmi to sdi converters are powered by the usb ports of the media players (small form factor PCs).
The sdi to hdmi converters are powered by the usb port of the TVs. All TVs are the exact same model.
All wiring and bnc termination has been thoroughly tested.

Any advice how to resolve the issue would be welcomed.
Thank you in advance

Im not sure about your wiring ..where is connected video hub ?

Hi Roman,
the video hub is installed in a rack, 40 TVs are connected to the video hub(they work perfectly)
The other 16 Tvs are connected on the 2nd SDI out port of the converters
What is the best way to check the wiring ?

Thank you

So out from video hub, to sdi to hdmi convreter .. hdmi to tv (this works) .. and sdi loop from that converter, to another converter sdi to hdmi, and hdmi to secondary tv ?
And this is 40x ?

Sorry i think i confused you.
40x Yes
Media Players - hdmi2sdi -videohub-sdi2hdmi-TV (this works perfectly)
Then from the 2nd sdi out of the hdmi2sdi we go to sdi2hdmi-TV ( those ones some times work , some other times dont)

Long cables ?
Videohub will do reclock and maybe more power ?

The cables are between 60-80 meters long, i will test with a usb hub to power the converters to see if anything changes

And check short cable .. 2m ..
60-80m its long for sdi output from converter i think ..
and u can try for test, swap sdi to hdmi microconverter to bmd bidirectional microconverter .. its doing reclock ..

In o2 arena Prague we had problem with long cables .. that cables everywhere works .. on thats place we got random blinks .. bidirectional converter not helped .. Decimator converter was help and signal was stable ..