Brewing stand not accepting water bottles

I've built the automatic brewing station from this tutorial. I've been through it three times to make sure I have everything as per the video, but things aren't quite working.

The full water bottles make it to the hopper than is pointing towards the brewing stand but for some reason they won't load into the brewing stand. I have a feeling it's something 'locking' the brewing stand (like you can lock hoppers), but that's just a guess. Here's a screen cap of the offending hopper;

The hopper is meant to be locked while the stand empties of the previous batch, but for some reason it never refills.

If it matters I'm on 1.11.2 and I'm playing on a server.

I do believe that the water bottle should be inserted from the top, as I do think that only the blaze powder can be added from the side (that was added before 1.11) hopefully this helps...