Boolean Subtract: different behaviour

ml

I intend to cut out a front plate for some connectors (of an electronic board)

So I imported the board with the connectors into a part studio and unioned there all together into only one part for an easier handling (all stays together) of it as a whole later in another part studio when mating.
The cylinder (blue) of a connector is also part of this (seen in the second part studio):

Now I would like to boolean-subtract it:

does not work.

ok.

because I was earlier able to do this, I've tried it this way round:
let the cylinder in the first part studio beside, and add the sketch and extrude in the second one (where mating):


this time the subtract works:


as expected, using the same settings of the boolean. 

but why? I am not aware of the specific design flow. Just thought it would be better to handle the board and its relations in one part studio and do the mating, subtracting in another to separate the tasks for a clear distinction.

thanks for any hint.

NeilCooke

What is the error message when you hover over the red dialog title? The offset is trying to offset every face of the board so it is probably failing there.

ml

message:

but did not select any face... (I think)

without 'offset all' it works while selecting the specific face: