Finish the sentence.
…the box art shows a figure in the hatch, but there’s no figure in the box.
…an X-Acto knife rolls off your bench, and you instinctively try to catch it.
…you apply Tamiya Extra-Thin only to find you’ve welded a perfect fingerprint in the opposite side of the part.
You glue something in the perfect position, only to find when you placed it down or left it overnight, it’s shifted a few mm and now wont fit into/onto what it was meant to…
When you knew you should have bought good aftermarket decals but didn’t…
Thinking old DML figures kits here, when you see fantastic Ron Volstad artwork on the box top but open it up to find something that only vaguely resembles it.
When you spend ages searching for an oop kit, pay a bit more than you want, only for it be reissued at a lower price.
You glue and clamp something together only you leave it too long and the clamp handily mis-aligns the part.
You crack the windscreen.
You mis-align a truck chassis.
You spill glue everywhere which starts to melt the cutting mat and everything else nearby.
or with better quality …
you realize your jet fighter model has about 1000 stencil decals
… you lose your train of thought while waiting for glue to cure! … Freakin’ sub-assemblies everywhere!
—mike 
I have perfected my knife rolling off the desk dance moves,probably would make cool youtube video.
When the small part your holding with a tweezer or cutting flys into oblivion never to be seen again,or maybe weeks after you completed the model.
……your finished project never matches up to what you started with in your head.
… my model looks 20 times better “without” paint… or is that 20 times worse “with” paint? 
… you scrape and sand sprue connections only to have them grow back on the part. 
… you scrape and sand sprue connections only to realize you’ve removed crucial detail instead.
… when my photos lie to me. 
… “There are no hairs, dammit!”
… but wait, there’s more! 
—mike
With me that’s all of them… I’ve learned to embrace it; scratch building sci-fi stuff means I only have a vague idea when I start and may not be certain what I’ve made when I feel it’s (sort of) finished.
Cheers
M
Waiting 40 years for a re-issue of the Airfix Beach Buggy, then they follow it up with the Bond Bug! Praying for the Ford Capri despite knowing they modified it for a custom version (actually I’d prefer that).
Cheers,
M
Sh***y vinyl tires melt the rims that you primed, painted and sealed with 6 coats. Dagnabbit… 
Jimbo
…the restoration of a 40 year old caravan takes far longer than anticipated, thus reducing time available for model making to an absolute minimum #happywife-happylife 
… when you realize the kit has vinyl tires …
I had that with my Dragon BRDM-2; I have build the same kit when i was still in the military ad saw the tires rip themselves apart. No more… I spend the extra cash this time for a set of DEF Models sagged wheels.
Yes! The buggy was very highly sort after.
Don’t usually do cars but I’m tempted to have a go at one. Something colourful and different.
Ah, that set might be a little harder to attach as it’s made for the Trumpeter. 35019 is made for the Dragon/Cyber Hobby/Zvezda kit.