G43 not being applied in g-code

Revisiting an issue I noticed here:

forum.linuxcnc.org/10-advanced-configura...l-orientation#345715

At the time I wasn't sure if this was a GUI issue, or something in my config.  I've since switched GUIs (Axis, FlexGUI, and Qtpyvcp) and the issue is the same across all three GUIs.

Problem I have is that G43 isn't being applied consistently during a program.  G43 works via MDI, and all three GUI tool-change buttons.

I've tried every permutation:
Tn M6 G43
Tn M6 G43 Hn
M6 Tn G43
M6 Tn G43 Hn

And the same as above, but with G43 on another line.  Also tried an M1 after the tool change line(s) - even a few lines down - but LCNC just isn't applying the tool offset.

When I run a program, LCNC excutes the tool change - new tool number is displayed in all three GUIs - but doesn't apply the offset.

Tool number doesn't matter - whatever tool offset was previously applied remains active after the Tn M6 line.

Under Axis I was using the "T" remap from the sim lathe-fanucy
Under qtpyvcp, I commented out the "T" and "M6" remap and was just using the 'stock' M6

I'm sure this is something on my end and unlikely to be an LCNC problem.  Maybe the remap.py and stdglue.py used by my other remapped M-codes is interfering with 'normal' M6/G43?

Anyone have an idea what would interfere with G43 being applied during a program, but not via MDI or a GUI-based command?