Ground Control MIDI Switching Issue

[somebodyelseuk]

Hiya
Hope someone can help.
I'm having a switching issue.
I'm using a Ground Control v2.4 floor unit and the problem I'm having is that the third unit in my chain isn't receiving MIDI info. I'm routing through a Mesa Boogie Triaxis, Digitech Studio Quad V2 and Digitech Studio Quad V4. The Triaxis is switching fine and the second unit is too, but no matter which way I route the second and third, the third doesn't receive. I tried three different MIDI cables between units 2 and 3.
Units are linked 'Thru' to 'In' and all Channels are setup correctly on the units and floor unit.
I haven't used the rig for a few months, but all was working fine back then and it has been stored at home in a spare room, so storage conditions aren't a problem. The only thing I haven't tried is reinitialising the FX units. I have all the units backed up so that will be my next step, unless anyone has any suggestions.

[domct203]

Are you still able to control the third unit if it is the only one connected to the GC? How about if you swap the positions of the second and third unit?

Is it possible that a setting for the MIDI thru on the second unit could have been accidentally changed? Do these units have a MIDI out as well as the MIDI thru?

Dom