Corner Pin transformation not smooth

Hello,

Any help would be appreciated.

I'm having trouble getting a smooth Corner Pin transformation in my animation.  I'm applying the effect in the main composition, to a pre-composition with many nested comps within it.  Graph editor shows a nice smooth arc between keyframes, yet I'm still getting an undesirable "popping" effect, where the transformation lurches here and there between one frame and the next.  It is not only present in previews, but in full res rendered footage as well.

Any thoughts as to why this is happening, and what I can do about it?

Thank you!

Here's what I'm using:

After Effects CC

iMac (Retina 5K)

Processor 3.8 GHz Intel Core i5

Memory 32 GB 2400 MHz DDR4

Graphics Radeon Pro 580 8192 MB