I believe this to be a problem with Epson printers and perhaps with all printers setting up custom page sizes. This has happen with VW 8, 8.5, 9 when using the Epson Large Format Printers (1200 series).
You have to be extremely careful when you define your custom page size, ie. 11x17, 13x19 for example. And it can be further complicated since Epson gives no clue how to do this. The problem has to do with the fact that the true size of the print is not the same as the name size
After defining the custom page size in Page Set Up--go to Page--Set Print Area--go to One Page and note the true size that VW designates. Your drawing must then be multiples of the height and width measurement indicated.
Good Luck