I have set up an SLA for Initial Response.

The only filter on this is that the request is to have a priority of Normal.
Most, close to all, request have this SLA stop when either we add a comment to the customer or a resolution is set.
However, there is the odd one that just has this SLA running even tho a customer comment has been added.

I am not really shore what additional information I can add but please let me know if I have missed something that will help in working out why some SLA's will not stop.