Something that happens to me more often than cards falling out during shuffling, is cards "sticking". by this I mean, for example:
if I am doing a mini three-card on - say home and family, and I lay one card for the present, a second card for the way forward, and a third card for the outcome. then, after they touch the table, you realise that one of those cards was actually two cards together, like turning over two pages in a book instead of just the one.
I used to separate them, but got messy and inaccurate readings. Now I read them as they are, and read - say - the Four Wands as the outcome, telling me that eventually she *would* find a suitable property and buy it, then shifting the Four Wands aside to find an Three Pentacles underneath, which led me to qualify it by saying that there was still work to do on the house, and in particular she may want to get structural engineers to have a look at the foundations.