Blueprint variables get reset if not made Public

When a blueprint variable is not set to Instance Editable, its value gets reset at runtime. This seems to occur because the variable OriginalCannonTransform seems to get reset/nullified after being set correctly at BeginPlay.

This issue was reported and tested in 4.19.2 (CL-4033788). This was reproduced in 4.20.2 (CL-4302132) and Main 4.21 (CL-4338396)

1. Download and open the attached project
2. Find the turret blueprint in the opening map
3. Simulate and click on the turret, it is possible to move around a 3D widget to set a vector location. This should direct where the turret is pointing
4. The moment you start moving the 3D widget, the Z value will be set to 0
5. Stop simulating and open the turret blueprint. Set OriginalCannonTransform to public/instance editable
6. Simulate and click on the turret again to move the 3D vector around

Results: The variable OriginalCannonTransform is getting reset to 0 when the variable isn't set to Instance Editable

Expected: The variable OriginalCannonTransform doesn't get rest.