Some types of videos won't play

Videos served from TikTok, Twitter or Vimeo sites will not load and playback. The initial image of the video will load, and audio will play with periodic stops. It appears to be trying to load enough data to continue playing. As long as I am patient, the audio will continue. The image, on the other hand, remains frozen on the initial image.

Note that videos from Paramount+, Peacock, Disney, etc. will play, as will all YouTube videos. So far, I have only found the 3 types of videos listed above that won't play.

I am running:

MacBook Air (13-inch, 2017)

macOS Monterey 12.6.1

8 GB Memory

250 GB SSD with 41.1 free space

My internet connection is provided by Spectrum @ "up to 400 Mbps", which tests to 140 Mbps *while the soccer match is streaming* to the Apple TV. I have no trouble streaming the entertainment services listed above under these conditions.

I am connected to the Spectrum modem through a LinkSys WRT 3200ACM running ExpressVPN.

I have already tried taking the VPN offline and viewing the videos. the performance does not change.

Again, note that only certain sources of videos do not play. All "major entertainment" sources play just fine, all of the time.

Any help would be gratefully accepted.