It's perfectly possible for something broken to work! Ways this can happen are many, and such things can be just hunky dory for the most common cases in the here and now.
When tolerances get pushed or corner cases happen, underlying brokenness shines through - quite often
to the detriment of those competent folks who have to fix it and those unfortunate users who reap the consequences.
I wouldn't dispute the practical merits of moving on when something works, but the fact a bridge is standing five minutes after the engineers have left, does not prove the bridge is fit for purpose!