The MIDI spec defines that MSB/LSB needs to be sent as a pair and must immediately followed by a PC (page 13, Bank Select)
However, a lot of implementations only require MSB or LSB.
The action however always takes place with receiving a PC.
So I would check the MIDI transmits with the Global MIDI monitor and the documentation of the Hydra.
A different approach/workaround could by a GP script, triggered by On Variation, reading out the widgets (now not mapped to MSB/LSB/PC) and create these and transmit the in the „right“ order
I used this in some early rackspaces to change presets of my Kurzweil…
Edit; have a look at https://community.gigperformer.com/t/patch-changes-on-external-midi-devices/9394