Programming an angle using sub-program

[pb2304]

I have a Mazak vtc-300c here using mazatrol and I am trying to program a 1.5degree angle over 50mm. As follows my program is

UNIT 1

MANU PRO FACEMILL 63
G0 G40 X-60. Y-6.5 Z100. M3
G0 Z10.
G1 Z0. F500.

UNIT 2

SUB PRO 22E REPEAT 72

END

SUB PROGRAM IS:
G91
Y-.35 Z-.009 F6000.
X120.
Y-.35 Z-.009
X-120
G90
M99
%

Now the sub program as it stands runs smoothly across the y z etc. Its the start point thats the issue, as shown I bring the cutter down to Z0. When it moves onto the sub program, the position changes and the Z moves to Z+150.141 and the the sub program begins from there.
There is nothing in the program that I can see that would cause it to move there. Not been on this machine long so unsure of what I'm missing?
thanks

[Guillaume89]

There is no G54, G55.., nor tool call in this program. Maybe that's the cause.

[RCaffin]

You should NOT have the G91 in the subprogram. Never (unless you really know what you are doing).
You could put it at the start of the main program.

Cheers
Roger

[pb2304]

The manu pro 63 is a tool call. The g54 came before unit 1, only added in what i felt was relevant.

[pb2304]

Took out the unit 1, created a separate sub program to be called in first to bring tool to position and it worked fine. I worked with siemens controls for 14 years before moving jobs and always had G91 at the start of sub programs, same as the fanuc I'm also using in my new job, I've used G91 at the start of sub programs as its an increment movement. Out of curiosity why should G91's not be used?
Thanks

[metalmayhem]

Out of curiosity why should G91's not be used?
Thanks

no reason why it can't or shouldn't be