That sounds like normal behavior. The sha1 folder is where the server caches downloads requested by clients. Even though you stopped the actions, the Relays will still try to cache the files that were requested by the clients and will trigger the downloads.
The sha1 folder may grow up to the size of
_BESGather_Download_CacheLimitMB. If that size is exceeded, a process will remove the least-recently-requested files from sha1, a task that I believe runs hourly, so the cache should take care of its own cleanup when necessary.