Projection Painting

Hi, i am trying to project paint onto a model of a cat using a selection of UV Maps.Not sure what i have done wrong? i have already successfully done both sides, the tail & from above, but when i have come to do the head it will not paint? i have tried re-making the uv map of the head but still will not work? i have noticed how ever that when i am in Texture paint mode my main colourmap which is visible in the image editor shows a grayed out map of the UV. on this grayed out map the head part is missing? but if i go into edit mode it is visible again. also if i choose my head UV map i can see it positioned and will paint correctly. i hoping it is something simple, and i am just missing something?
Can any one shed any light please?
Thanks in advance.

are you sure the coords of the head are joined to an image in all UV channels?

There is this button, you click and painting is limited to selected faces only…Maybe this?
In general, this crystal ball business is boring.
Have any workspace screenshots or something?