Can't Send VGA to InFocus D/A M1 Port

I'm having a problem sending a VGA signal to an InFocus IN38 projector's D/A M1 port. My ultimate goal is to use a DVI-I switchbox to switch between VGA sources and DVI-D sources. The DVI-D sources work fine. The desired signal path for the VGA sources is:

VGA sources >>> VGA-to-DVI adapters >>> DVI-I switch box >>> long DVI-I cable >>> DVI-I-to-M1 adapter >>> IN38 projector DVI-D sources >>> DVI-I switch box >>> long DVI-I cable >>> DVI-I-to-M1 adapter >>> IN38 projector

For testing, however, I've eliminated the box, the long DVI-I cable, etc. Here are the tests I've conducted:

VGA source >>> InFocus-bundled VGA-to-M1 cable >>> IN38 projector: Works as expected.

VGA source >>> ordinary 6' known-good VGA cable >>> VGA-to-DVI adapter >>> DVI-I-to-M1 adapter >>> IN38 projector: Projector searches indefinitely, pausing momentarily on M1 port before resuming search

I've purchased alternate VGA-to-DVI adapters (different brands, one from Office Depot and one from Monoprice) and I get the same results regardless of which ones I use.

The DVI-I-to-M1 adapter is from Lindy and is specifically described as such (as DVI-I, not DVI-D). I've exchanged this adapter, but I get the same results with the replacement. FWIW, I do have the pin-out diagram.

Technicians at InFocus and at Lindy both say that it should work. What am I missing?

I received a diagram from an InFocus Tech showing the pin-outs between M1, DVI-I, and VGA. Apparently, the projector requires a connection between M1 pin 4 and VGA pin 4. All five VGA-to-DVI adapters I've tried up to now omit the connection from VGA pin 4 to DVI pin 15. Since DVI pin 15 is the one that sends the signal to M1 pin 4, the end result is that M1 pin 4 and VGA pin 4 are not connected. Is it likely that I'll find a VGA-to-DVI adapter that connects these pins?