I have the following 3x3 square plane. I made a cluster (see Fig. #1) with 8 vertices and tried to rotate it along a static point by 90 degrees. I also made another cluster (see Fig. #2) with 4 vertices and this time I want to rotate it along a moving vertex by -90 degrees.

The first cluster rotation works well. However, there is a problem on the 2nd cluster rotation. The moving vertex point follows well in the vertical direction but it stretches out in the x-direction (see Fig. #3). I need to manually adjust the rotating vertex position in order to remedy this issue (see Fig. #4).

My question is what am I missing here? How can I avoid this manual adjustment? Thanks.