An employee repeatedly ignores a work colleague when approached on issues not related to work
. On the face of it this seems quite minor and also it's non work related. However if the context was that the work colleague was their line manager and the employee was ignoring them when they were simply asking after their welfare, such as how are your family? etc it puts it in a slightly different field as far as I am concerned. Not dismissal material, but certainly worthy of a chat and possible warning about attitude and conduct as it would seem to be an indicator of some other problem.