Not so much broken as hasn't been implemented. Let us get on it for you.
UltraNC30 Jun 2026
We have now added in G04 dwell support.
Dwell units are read as seconds, so G4 P5 equals 5s, which is how Haas, Mach and LinuxCNC behave. The exception is Fanuc, where a no-decimal P is milliseconds P5000 = 5s.
Dwell units are read as seconds, so G4 P5 equals 5s, which is how Haas, Mach and LinuxCNC behave. The exception is Fanuc, where a no-decimal P is milliseconds P5000 = 5s.
(UltraNC - G04 dwell test)
(T1 D=6.0 - 6MM FLAT ENDMILL)
G21 G90 G17 G94 G54
T1 M6
S10000 M3
G0 X0 Y0 Z5
G1 Z-1 F300
G1 X60 F1000
G4 P5 (5s dwell)
G1 Y40
G4 P0.5 (0.5s dwell)
G1 X0
G4 P2 (2s dwell)
G1 Y0
G0 Z5
M5
M30