It is believed that soft references resolved during runtime, point to the edit time instances of actors instead of the runtime instances. This issue does not reproduce when it is called from an Input Binding, only from a Widget. A work-around for this is to insert a 0.1 second Delay between the OnClick and the Transformation function.
This was reported and tested in 4.20.2 (CL-4302132). This issue was reproduced in 4.19.2 (CL-4033788) and Main 4.21 (CL-4309299)
Results:The Cube doesn't move when the button is pressed
Expected: The Cube moves when the button is pressed
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-63285 in the post.