I have a similar setup here. To me, it sounds like the bottleneck is at your Reflex Merge function of its MIDI IN (MIDI OUT is not acting as a MIDI THRU). Have you checked its MIDI IN Channel? Press the footswitch long enough to get past the treadle CAL, getting to CH(x) in the display.
Even that doesn’t ‘feel’ right, unless an upstream MIDI message from the MC6 Pro is changing your Reflex program unnoticed, somehow.
You’re running a moderately complex MIDI system, so fortunately, you have a lot of routing options to get around most anything.
I don’t think this is the core issue, but in my view, you are well past the limit of reliability with daisy-chained MIDI. 3, rarely 4 devices THRU for data corruption.
You don’t need a separate MIDI THRU box. It’s all in creative routes with the MC6, and how you connect your devices to it.
I’m out of town, so let me see if I can recreate the issue with the Pro, Reflex, H90 plus a couple more devices, and possibly offer a more solid solution.
