Fire trucks not spawning in backup

Ive tried with standard lspdfr backup and then ultimate backup. I've spoken to the developers of ultimate backup and we've established its not the plugin.

For some reason whenever I try to call backout, no matter which way I do it, fire engines simply do not spawn.

They spawn normally at the fire stations and with rage etc, they simply just dont respond to backup requests. I'm using the greater manchester fire technical rescue one. 

I'm not so great at these forums so I apologise to the admins and moderators if I've chosen the wrong forum to post this in.