[sass11]

On my 1999 Haas VF-2 have flowing G54 position. Numbers are not changing itself, but every time I start to mill, work offset is in different place, difference is sometimes 0.1 mm, sometimes 1 mm.
Coordinates are set to vises corner and every time I start to mill, corner shows different coordinates, but shift is never more than 1 mm.
During milling, coordinates are not flowing anymore, everything is accurate. On next job, G54 is flowed again. Mill restart and all zero does not help.
Of course old machine has some backlash, but not so much, because milled pieces are fine.
Any ideas?

[mactec54]

On my 1999 Haas VF-2 have flowing G54 position. Numbers are not changing itself, but every time I start to mill, work offset is in different place, difference is sometimes 0.1 mm, sometimes 1 mm.
Coordinates are set to vises corner and every time I start to mill, corner shows different coordinates, but shift is never more than 1 mm.
During milling, coordinates are not flowing anymore, everything is accurate. On next job, G54 is flowed again. Mill restart and all zero does not help.
Of course old machine has some backlash, but not so much, because milled pieces are fine.
Any ideas?

Check the Home switches it sounds like you may have some chips behind the covers, that is changing the homing position, worth a check