WebVtt captions display for HLS Live stream with 10s segments, but not for stream with 3.8s segments

The setup:
Our customer has a live HLS stream, with 10-segment duration, with VTT subtitles. When playing this stream in the Androidx Media demo, the captions can be selected and displayed. The customer wants to use a shorter segment duration (3.84s), however, for the stream that plays these shorter durations in the demo, captions can be selected, and show in the tracks log output as selected, but do not display.

There are no errors written to the logcat.

I've also observed this behavior with ExoPlayer 2.19.1 (which our SDK is currently using; we are planning to migrate to AndroidX Media later this spring).

I've noticed with the customer's 10s segment feed, that the captions displayed appear to have some minor sync issues with the spoken dialog.
(both 10s and 3.84s URLs will be shared through the dev email)

Questions:

1. Considering that there are no errors seen in the demo app's logcat, it does not appear that this is a bug, would you agree?
2. Considering that we're still using ExoPlayer with our SDK, are there any ExoPlayer configuration parameters that might help with this behavior?
3. Based on this behavior only occurring with the shorter segment duration, we're going to suggest to the customer to test with somewhat longer segment durations, is there a segment duration (less than 10s) that you may have seen elsewhere, where this behavior did not occur?

Thanks in advance for your assistance.