If you build an auto fish farm, you're gonna end up using string and tripwire hooks to determine when the bobber catches something. Unfortunately, as the bobber moves up and down, it actually bobs below the tripwire, meaning auto fish farms don't work properly. I'm not against it bobbing in the first place, but it does need to be lessened. If this is working as intended, please change it.
This bug is fixed in the latest beta version, and the fix will be included in a future update when that is ready for full release (no specific date can be given). We will leave this ticket open as a point of reference until the fix has been fully released.