MIDI from Cubase vs MIDI from hardware, syncing x0x boxes problem

This may be a general MIDI curiosity more than a Cubase issue but it only started when i brought Cubase in. Bottom line is my Din Sync boxes lag behind the MIDI boxes, but only when Cubase is the midi master.

Banana Split = a midi splitter
Synchole = midi to Din Sync splitter
Beatstep Pro = hardware sequencer
(Banana Split and Synchole have always been good!)

Here is what worked well before Cubase.
Beatstep Pro master (BSP):

BSP midi ->Banana Split
Banana Split midi thru -> Synchole
Banana Split midi -> 727
-> Synchole Din Sync --> 606 & 303
All midi and Din Sync boxes play perfectly with BSP as master.

Then I put Cubase as master, in front of Beatstep.
Cubase Elements 10 via UR22 as master:

UR22 midi -> Beatstep
->Beatstep midi->Banana Split
Banana Split midi thru -> Synchole
Banana Split midi out -> 727
-> Synchole Din Sync -->606 & 303
Now they all play but 303 + 606 slowly fall behind.

Here is the twist:

Without changing anything at all from the above setup, I switch Beatstep from midi slave to internal clock again, press play on Beatstep all stay syncd again.
I can put 727 midi out into Synchole and all stays syncd…

Then I make BSP slave again and hit play on Cubase, and din sync lags behind.

I also tried taking all midi stuff out, to remove beatstep and Banana Split from suspicion.
Cubase UR22 midi -> Synchole Din Sync -> 606 & 303:
the boxes drift apart from each other even you can see on cubase visually the beats are going by faster than the 606 is playing. Put Beatstep back in place of cubase and everything stayss syncd again.

MIDI boxes playing their own internal patterns like 727, stay in sync fine with Cubase UR22 midi. So the midi is good enough for that.

conclusion / mystery

Synchole is technically just as suspect as Cubase, but there is a funny difference between the midi out from Cubase, and the midi out from the beatstep, which affects the Din Sync converer behavior. and midi from cubase is less good somehow.

If anybody has any thoughts Id be so grateful.
I thought of midi time resolution, maybe Cubase is set to something that is confusing the Synchole but Beatstep isnt… but I dont know and not zure how Id measure it. I wanted go use Cubase and compose a piece using 606.

Thanks for reading I know its too much!

I tried a Doepfer MSY2 midi to din sync instead of Synchole and this seems to work. At least there is a workaround.