OEMTextOut glyph position problem

We are writing a special plotter driver and we are seeing some
strange things when we are looking at the GLYPHPOS structures being sent to OEMTextOut call…
The glyphs start out their position correctly but at some point we get a negative Y coordinates or the offsets for the Y coordinates restart at low numbers and all text lines are getting mixed.

We noticed that it starts happening when Y > 7200 in
*PrintableArea: PAIR(7200, 7200) of GPD file

We need to support big table sizes 48x48 inches and have to have a good text quality for small fonts so we need to set
*DPI: PAIR(1200,1200)
*TextDPI: PAIR(1200, 1200)

If we set DPI for lower number Windows programs like Corel returns low quality Text. Setting DPI for low resolution but TextDPI for high resolution doesn’t make text better. Are there any limitation on DPI * Y Size?

Any help would be greatly appreciated.