What you describe is not 'normal' but neither is it entirely unknown either. In fact I think certain manufacturers are actually encouraging scratch building...
A conventional plastic kit manufacturer expects to have a production run of many thousands and will invest heavily in injection moulding to achieve it although they do often get detail wrong.
A model boat kit will have a much, much lower production run from a much smaller manufacturer. It's quite possible that only 5 of your particular kit might be sold in a year depending on its popularity. So yes, it isn't possible to put the level of development into these kits that the plastic kit manufacturer does. And then of course there is much more building input required of the purchaser of a model boat kit. Having said that, there is no excuse for poor quality control and failure to remedy faults that occur during the kit development process. The kit you have could have been so much better had just a bit more attention been given to bring it to market. A lot of the problems could have been very easily corrected.
Certainly not all kits are like that, not even from that particular manufacturer. At the other end of the spectrum, last year I built the SLEC kit of the Fairey Huntsman 31 which was designed by Dave Milbourn for a Model Boats magazine review. I can honestly say that there was virtually nothing whatsoever to criticise about it. The only nit picking I could muster up was a recommendation to silver solder the pulpit railing which I thought might be a bit beyond the average builder (Dave and I have amicably agreed to differ on this) and truly minor points such as making the anchor from sheet wood when maybe plasticard might have been easier to get a metallic looking finish on. It really was scratching around as the kit components fitted together beautifully and the instructions were exemplary, everything you need to know is in there as long as you read them including recommendations for running gear, motor and batteries etc. And following the recommendations for powering the model gave a really exciting experience.
The kit is tried and tested in that after designing it, Dave actually built examples to satisfy himself that everything in the production kit fitted together as intended (as do most manufacturers) which I'm afraid wasn't the case with your model where only a pre production version was probably made - hence the difficulties you are experiencing.
Colin