Error combining cutter compensation (G41/42) with work offset (G55)

Hi all,
At 19:55 in this video...

 

I was making a set of lathe tool height adjusters, and used a loop with G55 to repeat my tool paths along a piece of stock. This worked great for engraving and drilling such as this code...
o100 Sub
 G0 X0 Y0
 G0 Z5
 G01 Z-2 F100
 G01 Y-14.5 F1000
 G01 X10.5 Y-20 
 G01 X21
 G01 X30 Y-14.5
 G01 Y0
 G01 X0
 G0 Z50
o100 endsub

#50 = 0
G17 G21 G54 G90
; OP 1 engraver outline
M6 T16 G43; Drag engraver

o110 while [#50 LE 5]
    G10 L2 P2 X[#5221]  Y[#5222 -23* #50] Z[#5223]
    G55
    o100 call
    #50 = [#50 + 1]
o110 endwhile
M2

However, my last tool path was a 10mm endmill to cut the contour, and I just reused the engraved path and added G42 to cutter comp it. This errored out with Linuxcnc throwing this message.
 

Here is the code...
o100 Sub
 G0 X-10 Y0
 G0 Z5
 G01 Z-2.5 F100
 G01 X0 Y0
 G01 Y-14.5 F1000
 G01 X10.5 Y-20 
 G01 X21
 G01 X30 Y-14.5
 G01 Y0
 G01 X0
  G01 Z-5.5 F100
 G01 X0 Y0
 G01 Y-14.5 F1000
 G01 X10.5 Y-20 
 G01 X21
 G01 X30 Y-14.5
 G01 Y0
 G01 X0
  G01 Z-7.75 F100
 G01 X0 Y0
 G01 Y-14.5 F1000
 G01 X10.5 Y-20 
 G01 X21
 G01 X30 Y-14.5
 G01 Y0
 G01 X0
  G01 Z-10.5 F100
 G01 X0 Y0
 G01 Y-14.5 F1000
 G01 X10.5 Y-20 
 G01 X21
 G01 X30 Y-14.5
 G01 Y0
 G01 X0
 G0 Z50
o100 endsub

G17 G21 G40 G54 G90
M6 T10 G43; 10mm end mill
G42
G0 X-10 Y0
G0 Z50
M1
S3000 M3
G4 P4
#50 = 0
o110 while [#50 LE 5]
    G10 L2 P2 X[#5221]  Y[#5222 -23* #50] Z[#5223]
    G55
    o100 call
    #50 = [#50 + 1]
o110 endwhile
M5 M9 G40
M2

Is this just a simple error on my side? I didn't find anything in the reference doc's on cutter comp and work offsets not working together.
Cheers,
Mark
 

You're missing a G40. 

There is one at the end Should there be another?

No, G40 must come first.A change is only possible without tool compensation. 
G40
...
G52