No module named errors setting up two different integrations

Specifically, afrer adding breaking_changes and spotcast to my Home Assistant installation separately, via HACS, I get these errors in the logs:

2021-10-09 16:58:58 ERROR (MainThread) [homeassistant.config] Package homeassistant_version_package setup failed. Integration breaking_changes No module named 'integrationhelper' (See /config/packages/homeassistant/version.yaml:9).
2021-10-09 16:59:05 ERROR (MainThread) [homeassistant.config] Package media_spotify_package setup failed. Integration spotcast No module named 'spotify_token' (See /config/packages/media/spotify.yaml:6).

The traditional solution to this, I am given to understand, is to restart Home Assistant a few times and it will install the needed dependencies. Well, it’s been more than a few times, and no joy - but more interestingly, if I look in the deps subdirectory under my config directory, I see this:

total 328K
drwxrwx--- 2 swarm users 4.0K Sep 21 14:57 hacs_frontend-20210822172723.dist-info/
drwxrwx--- 3 swarm users 4.0K Oct  9 11:54 integrationhelper/
drwxrwx--- 2 swarm users 4.0K Oct  9 11:54 integrationhelper-0.2.2.dist-info/
drwxrwx--- 3 swarm users 4.0K Sep 22 07:33 iso8601/
-rw-rw---- 1 swarm users 2.5K Oct  6 14:11
drwxrwx--- 2 swarm users 4.0K Oct  9 11:54 spotify_token-1.0.0.dist-info/
-rw-rw---- 1 swarm users  957 Oct  9 11:54
drwxrwx--- 3 swarm users 4.0K Sep 22 07:33 test/

which it to say, what looks like these modules installed next to the various other dependencies for my various other integrations, all of which are loading and running just fine.

Any thoughts on where I might go from here to debug this would be much appreciated.

(HA 2021.10.0, and HA 2021.10.2, container version running under Kubernetes, FWIW.)

A curious twist, incidentally:

The configuration checker indicates the configuration to be valid as long as those dependency files are in place; delete them, however, and it indicates that these integrations can’t be set up because of missing dependecies. So at least part of the system is able to find them…