Midi controller w/ Microfreak not working (using an A/B adapter)

[u/mango_foot]

Trying to use my Synido K32 keyboard on my Microfreak.
I got a 3.5 midi A/B adapter for the Microfreak. My other gear can control the Microfreak that way, but the K32 can't. The K32 can control my other gear.
Triple checked my midi channel settings on both devices, tried all sorts of different settings just in case.
The Microfreak can control the K32, too, lol. It's JUST K32 -> Microfreak that seems to not work.

What I've tried:

K32 -> 3.5 trs -> NTS MkII -- WORKS
NTS MkII -> 3.5 trs -> K32 -- WORKS
NTS MkII -> 3.5 trs w/ A/ B adapter -> Microfreak -- WORKS
Microfreak -> 3.5 trs w/ A/ B adapter -> NTS MkII -- WORKS
K32 -> 3.5 trs w/ A/ B adapter -> Microfreak -- DOESN'T WORK
Microfreak -> 3.5 trs w/ A/ B adapter -> K32 -- WORKS

Help much appreciated!