Video publish/export forces small target size - and failure to publish

I’m running Lightroom Classic version: 11.2 [ 202201281441-a5b5f472 ]

with the latest version of SmugMug plugin; on MacOS 12.2.1.  I’ve had persistent errors in uploading some videos in one of my galleries - a gallery that successfully uploaded many other similar videos.  See below for the (not particularly helpful) error message and some parameters of one of those videos as well as the publish/export settings when that video is selected.   I've iterated with SmugMug support but they say this is a function of Adobe & Lightroom: some videos that are 480x640 (or 640x480) are properly exported/published to H.264 at 480p, and others (like this one) are inexplicably targeted for 320p... which is too small for SmugMug to accept.  They claim it is an Adobe bug.

If not, what is the reason, and the workaround?