positioning error

[kendo]

I'm getting a positioning error when making two cuts at opposite ends of a long part
you can see in the code below,
T20 comes to the right end and makes a cut in X at Z-.44
then it retracts,
changes from G54 to G55 and cuts the other end at the same depth
problem is, its not going to the same depth
the G55 cut at Z-.44 is about .09" shallow

theres nothing in the Z column for both work offsets
theres nothing in G52
same tool, same depth, different work offsets
and nothing I can tell that should make the G55 cut shallow
I had to program G55 to cut at Z-.53 to get this part right

(1/2" ENDMILL)
T20 M06
G91 G28 Z0.
(RIGHT END)
G00 G90 G54 Y0.188 X-0.35
M03 S6000 F36.
M102 I0.05 J1.5
G43 H20 Z1.
G00 Z-0.44
G01 X-1.5
G91 G28 Z0
(LEFT END)
G00 G90 G55 Y-0.188 X-0.35
G00 Z-0.44
G01 X-1.5
G91 G28 Z0 M05
M103
G28

[kendo]

I got it to work by adding
G43 H20 Z-.44
after the switch to G55
is this supposed to be necessary?
I thought a TLO stayed active untill a different one was called

(1/2" ENDMILL)
T20 M06
G91 G28 Z0.
(RIGHT END)
G00 G90 G54 Y0.188 X-0.35
M03 S6000 F36.
M102 I0.05 J1.5
G43 H20 Z1.
G00 Z-0.44
G01 X-1.5
G91 G28 Z0
(LEFT END)
G00 G90 G55 Y-0.188 X-0.35

G43 H20 Z-0.44

G01 X-1.5
G91 G28 Z0 M05
M103
G28

btw, I can't get font color to work, clicking the drop-down arrow does nothing