Repetier firmware skipping first steps (1 reply)

When I run the attached short gcode program it skips the first approximately 50 steps but then carries on till the end correctly. The file is just to use the 3D printer as a pen plotter and mark out its own heated bed for etching. What is plotted is a Hilbert curve and was produced with a spreadsheet. I think I have included all needed codes but there is something wrong.

Edit: Whoops! the version I attached here did not have the preamble. The one that I ran started with:

G21
G28
G90
M82
and the first G1 line ended with F500 to set the speed.

Thanks for any help you can give,

Mike