This has been an issue for some time, but now documenting here.
@demeritcowboy says this fixes it in CRM/Utils/Hook.php :
It's not a very efficient hack. I think I meant to try to fix it better in core and then got sidetracked.
- $fnNames = $this->cache->get($fnSuffix);
+ //$fnNames = $this->cache->get($fnSuffix);
+ // skip cache because otherwise it skips drupal modules hooks
+ $fnNames = NULL;