In this kind of scenario it’s hard to give you a clear answer without a full assessment of the dog and watching it at work.
The dog obviously knows what to do but on occasion she fails to do it.
Is it out of excitement?
If this is the case then it’s in order to keep reminding her of what is expected of her – I’m often to be seen talking to my dogs so they are clear at all stages what they are meant to be doing.
However, if she still fails you will need to be ready to intercept her as she runs in!
Finally, don’t discount the possibility that on occasions she may simply misinterpret you – something that can even happen when you start to talk to a neighbouring Gun.
In instances like this the dog reads your words as a command.
Observations into what triggers her behaviour will be key in stopping it.