A user reported a problem with the latest lockdown, 3.43.022, and I was able to duplicate it.
Mach3 will freeze up during a toolchange, when it asks you to press the Cycle Start button.
The M6Start and M6End run fine in the VB editor, but Mach3 hangs at the start of the M6end during a toolchange.
Until I can get it resolved, I recommend using 3.42.040 with this screen.