This is admittedly a bit of a shot in the dark, but it looks as if the hot water is turned on and the cold is not. (This based on the position of the shutoff screws)
If the hot is on and the cold is not, the cartridge would close flow so all hot water is not passed to the shower head and a possible scald occurs. It is doing it's job. this This also explains why another cartridge does the same thing and why having no cartridge allows water to flow.