It's not for me to tell you what you should do, but I would suggest that is worthwhile becoming sufficiently familiar with model constructions so you can open them up and fiddle about with confidence to make them work properly. It's a great path to cheaply acquiring useful models.
Either fixed for a discounted 'sold as seen' item on their stand at a show, or dismantled to stock their spares supply. Both useful features of this brand's operation.
Assuming you are in the UK, customer protection means no trouble at all. It's been 32 years since I resumed buying new model railway products (the usual mid-life break!) and over this period I have had no difficulty returning for refund every 'not fit for purpose' new purchase from retailers - all of them with bricks and mortar premises - and the really good news is that the failure rate has reduced significantly over the years. (I am in the process of returning a model railway product at present, handled courteously and promptly by the vendor, and this is after a gap of five years since the previous such event.)
That's not to say everything is perfect. But since my most recent RTR OO loco failure (2004, Hornby Q1, split axle gear: by agreement between us the retailer obtained from Hornby a complete spare wheelset which I fitted myself) there have been no failure defects requiring replacement parts to fix, in any of my new loco purchases. Plenty of aspects needing attention for optimal performance, which I have dealt with over the years: wiper pick up adjustments, poor wiring arrangements, insufficient weight for traction, wayward springing on carrying wheels, topping the list.
Now some will say 'We shouldn't need to do any of this'; but here's the rub, we still get RTR OO for less cash than the comparable HO from the same manufacturing base. I'll take that saving, thanks: a little learning of the 'how to' goes a long way.
