I suppose it depends on how you define errors and 'goes together'......
If you have two cab sides that are not the same length, height or windows in alignment then I'd cal that an error, if however you don't mind lopsided cabs with wonky windows, then the kit is perfect.
To be fair the chassis on both engines is robust and forms square straight and rugged units. Once you add the bespoked etched valve gear and motion brackets it looks much better, same for the brake gear. Sand boxes are just white metal blobs, cylinders are grossly over scale and something like 4-5 mm too wide and outside of the loading gauge.
On the upper works the kit only supplies the lower front tank so if you want the taller one it's all scratch building, the rear end supplies the normal tank and coal space, no idea of the accuracy of fit of bits as it all went in the bin. The bits for the rotary tank are sparse and not the right profile so you might as well build all new. The actual rotary bunker is laughable, some cast ends and a simple cone with some overlay doors (half etch details back to front, aka rivet aid holes on the outside). There's no support at the front end and I think the rear end bearing was some gash white metal affair.
The boiler unit is probably the most usable aspect, there's no smoke box saddle to speak of and no way to support the front end, the firebox forms up okay but the boiler and smoke box are simple brass tubes that slip over each other, the material is so think you can't get any heat in it, I ended up using a plumbers torch and wicking in some solder to hold it.
The ash pan was useless so you'll need all new there and there's two maybe three pieces for the brake stay and cylinder mounts, they're all the wrong size and shape so up to you if you want to fit them. Most of the pipework is white metal, none of it fits is of the right profile or follows the real engine routing.
Cab is wonky and limited detail, cab roof is overly thick, wrong profile and...just ridiculous to work with.
Out of the box you can sort of build a Garratt, you have to accept it'll be out of gauge, incorrectly scaled, gaps in some parts, slightly lopsided and proportioned badly, at the bottom of a garden railway 20' away it'll look good.
There are people who have built the kit and think it's just fine, I'm not here to berate their efforts, standards or their visions, we're all different and I'm genuinely pleased they are happy with it; I wasn't, but then my build criteria is somewhat different.
If it wasn't for the advent of 3D printers and the clients ready acceptance/support to explore and use the new medium, then this kit would have remained still born. It's taken over two years and even within that time 3D prints have grown in detail, quality and strength; the extended gestation period has actually been beneficial as some of the parts (rotary bunker engine) would not have been as detailed/accurate or possibly even printable on earlier printers.
Having said all of the above, it must be remembered that the kit is old and comes from a day when modifying and scratch building was more accepted and part of the journey. It's also a time when access to works drawings at the NRM probably wasn't as easily accessible as it is today, let alone user groups, face book groups and the mass of free information on the internet.
Today with modern CAD and etching, casting and such like we can design and build NASA quality models, back then kit design was metaphorically stone age in a cave, there is only so much detail and fit that can be achieved with a burnt stick and sharpened rock.
