it would be a problem!
but did youdo continuous documentation thoughtout the year??
aslong as you have ur portfolio detailing the process of creating your project towards the final product youshouldn't be too worried..
i would state within your evaluation how the problem came about... and why thep problem could not be erradicated in time for the final marking..
eg. th wiring within the circuits had all been burnt, and if i tried fixing this problem, it would take a much longer time and there were serveral complicated issues that needed to be delt with??
that's just an example.. it problably is abit dodgy.. but never-the-less it may guild youtowards how and why your project didn't work!
as long as you have your portfolio showing the importent features such as processes, evidence, evaluation etc.. you should get some marks
(i didn't really finish my project but i still scored 89 for it because i documented well)