The problem is that what you are buying is a relatively inexpensive off the shelf Sellita movement in a designer case. You would think that as it is primarily the case and dial you are paying for they might make a rather better job of it, as it is I have little doubt both case and dial are probably made in China. I love all the blurb on their website about the founder being inspired by early one handed clocks. The only reason very early clocks only had one hand is because they hadn't yet worked out how to add a minute hand. What you have is a two hand movement with a big blank boss on the hour hand so you can't see the arbor for the minute hand that is part of the movement, and is still there ticking away out of sight, In horological terms it's a lash up. The likely problem with your watch is that the Sellita movement has a calendar complication, the date ring. They have them come up with some way of driving the inner day ring from that, and it is this non standard part of the movement that has failed.
If you want a mechanical watch you are far better to buy one from a maker who actually makes the whole watch, or at least has the common sense to leave the movement alone. Here you have a £150 movement (and that is what I can buy one for, you have to wonder what they pay if they are buying hundreds of them) stuck in a case and fitted with a dial and a nice looking strap, which probably cost between them no more than the movement, and a price tag hung on it for what, £1500? You might like the look of it, and if you are prepared to pay that much for the appearance, then hey, its your money. Just don't kid yourself it's a quality watch, or that it in any way represents value for money.