You may want to try deleting the field completely and re-adding it to the report. I know you said you've tried all of the various fields relating to the page number, but I'm not sure if you deleted the field and added a new one, or just changed the existing field. I've seen many corrupted fields regarding display formatting, though admittedly none that have caused this problem.

The only other thing I can think of is that the report group may not be defined properly.

In the spec designer, under the Report menu choose Groups. Make sure that it has plnVendor.OrdVend as the group being used (see the screenshot I've attached to this post).

If that's already setup properly, I'd suggest contacting your dealer who can take a closer look for you.