It's me again.
I've tried piggybacking 3x27c322 in order to gain a 12MB game. The problem is that only the first EPROM is being loaded, no switching happens here. Here's my setup for the 74LS139:

Pin 01 - /CE (cart connector)
Pin 02 - A21 (cart connector)
Pin 03 - A22 (cart connector)
Pin 04 - /CE of ROM 1
Pin 05 - /CE of ROM 2
Pin 06 - /CE of ROM 3
Pin 07 - NC
Pin 08 - GND
Pin 09 - NC
Pin 10 - NC
Pin 11 - NC
Pin 12 - NC
Pin 13 - VCC
Pin 14 - VCC
Pin 15 - VCC
Pin 16 - VCC

This also happens when only 2x27c322 are connected.

What is wrong here?