Odd dimensions/cropping on 'fp-small' thumb

[adambundy]

FdnPress 2.10.4
WP 5.1
Hosted on WPengine

I have been wrestling with very weird image behavior on this install. Client reported 'distorted' images after embedding, and sent screenshots. I couldn't reproduce until I was looking in the media lib, specifically at the 'fp-small' thumb of an image which my client had created and uploaded. Its quite large at 3000x3000. The other images seem to have generated fine though. I even copied the images and resaved them as JPGs, ran them through ImageOptim to hopefully remove any possible corruption. Same problem.

Oddly, this re-saving seems to have fixed the issue with one other image for which this was happening. Update: tried re-saving the original image in question at a smaller original size (1800 square), and the FP Small thumb looks good now. ?? Not sure if this is something in /lib/responsive-images.php (looks good to me), something in WP, or was just a glitch at time of upload and thumb generation.

Attaching screenshots of Image Details showing what the original 3000-square version looks like, and the distorted FP Small version. Both the original and re-saved large versions of this image distorted in the same way.

original: https://imgur.com/a/ae1vGH3
distorted FP Small: https://imgur.com/a/dHDQ5OV

Thanks!!