The "Belay Failure whilst Abseiling" mission has 2 variants, one variant requires the deployment of a Coastguard Rescue Helicopter, the issue, Bluewater units (including Coastguard Helis) cannot be dispatched to this call, making it impossible to complete.
The call is highlighted in red, the 3x Heli stations highlighted in yellow have multiple available coastguard helis, there are certainly multiple both free and close by that could be attached to this call. Its simply impossible for this call to be completed