We're using a HiCON Integra motion controller (with the corresponding plugin). It happens when we're running GCode; the specific code is as follows:
G91 (Relative)
F5
M24
G4 P2
(Layer 1)
M25
G1 Y-2
M26
G0 Z1
(End)
M27
The MCodes all call lua functions that send specific messages using UDP sockets to a seperate Python script. More specifically, M24 checks that a periphery machine is ready and M25 turns the machine on. We recognize the error when it occurs because rather than check the machine (M24), wait two seconds (G4 P2), then turn it on (M25), it checks the machine (M24), skips the pause (G4 P2), turns the machine on straightaway (M25), and then disables Mach4.
The error does not happen consistently. It seems to happen only once per day; typically during the first run of the day. It is alarming that it would just "skip" the pause and turn on the machine without a waiting period. In some applications that require a waiting period, this could be dangerous.