DDS Drawer Keyword

I'm developing a program that needs to switch between different paper drawers (different drawers have different colored paper.) and I'm having a problem that I can't figure out.

My program does the following, all in one spooled file.

-- Print a copy from drawer 3 (Using DDS drawer keyword, and a P-field).

-- Print a copy from drawer 1 (Using DDS drawer keyword, and a P-field).

-- Print another copy from drawer 3. (Using DDS drawer keyword, and a P-field).

I have gold paper in drawer 3, and white paper in drawer 1.

Unfortunately, my copies come out gold, white, white. So it's setting the drawer correctly for pages 1 & 2, but not for page 3! Here's the DDS:

A R INVOICE1F DRAWER(&PRDRAWER)
A PAGRTT(0)
A DUPLEX(*NO)
A OVERLAY(LIBSCK/INVOICE 0 0)
A FONT(011)
A PRROUTE 2 POSITION(0.940 0.600)
A PRSTOP 4 POSITION(0.940 0.875)
A*
A PRACCTNOTE 25 POSITION(1.429 .500)
.
.
more fields follow

I don't understand why. Why would it switch for the 2nd page, but not the 3rd? I've verified that the correct values are set in the PRDRAWER variable for each page. I've also verified that the DRAWER keyword is only sent on page boundaries, and nowhere else.

The printer is an HP LaserJet 4350, and I'm using Host Print Transform with MFRTYPMDL(*HP4) -- which is what IBM recommends.

I know that I can solve the problem by generating a separate spooled file for every page -- but this application would result in thousands of spooled files, which would would be extremely awkward for the user. (Whereas switching the drawer in the middle results in only one spooled file to manage.)

Does anyone have any ideas?