> * Strange error: "Error: Open(/home/runner/.cache/actcache/bolt.db): timeout"

This will occur if you have a `forgejo-runner daemon` running while you try to use `exec` -- both are trying to open the cache database, and only the first to open it can operate. You could avoid this by changing the cache directory of the daemon by changing `cache.dir` in the config file, or run the two processes as different users.

> It's a bit strange there are two files IMHO.

The `.runner` file isn't a config file, it's a state file -- not intended for user editing. But yes, it's a bit odd.