Planar reflections with any value lower than 100 for SeparateTranslucencyScreenPercentage are skewed/distorted when moving the camera, not representing the correct image when the value is 100.
Pre-requisites: project settings for Global clip plane for planer reflections must be enabled
1 - Prepare a mesh plane serving as water surface and apply a translucent material applied to it
2 - Attach a planar reflection component to the plane made at the step 1
3 - Prepare a mesh with any shape with a material of translucent or alpha composite applied to it
4 - Place the mesh made at step 3 in a position where it can be reflected by the water plane made in step 1
5 - at the console type r.SeparateTranslucencytScreenPercentage 100
6 - hit play and check the reflections on the plane made at step 1 are OK for any opaque mesh in the scene and for the mesh made at step 3
7 - at the console type r.SeparateTranslucencyScreenPercentage 50
8 - hit play and check that reflections on the plane made at step 1 are OK for any opaque mesh in the scene and that it is not OK for the mesh made at step 3
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-97218 in the post.