I have a situation I am unclear how to approach. Our hybrid working policy is non-contractual, and includes clauses stipulating that we may withdraw hybrid working for employees who are not performing when working from home. After 2 years this has finally happened - a member of staff is often uncontactable when WFH (disappears for hours on end) and quality / output of work declines - noted by 4 people that she supports. We had a conversation this week and have said that we are suspending WFH for her as currently it appears to not be working, and will provide assistance and guidance if she is having any issues with the work she is being asked to do. She has emailed me to advise that she feels we are being unfair , she is performing well and that she will continue to WFH, ignoring our instruction. She's been with the company less than a year. Any tips?