Last year, I bought two pairs of Merrell boots: A "normal" pair and a winter pair (bit more insulation, and some extra-grippy bits on the soles).
Unfortunately, trial in the store was not long enough and/or was too distracting, but on both -- different models -- the "box" of the left boot is narrow than that of right. And over the course of a few hours and/or more extensive walking, this causes my left foot to hurt from the constraint. Meanwhile, my right foot is perfectly cosy and fine.
This is not something I have experienced regularly with other brands. For some reason, that season, Merrell seemed to be making lefts smaller/narrower.
(Unfortunately, I ended up severely ill for a couple of months, two days after purchase. By the time I was well enough to consider returning them, I was too embarrassed at the time passed. And I'd gotten them on quite a good combination of sales, meaning that the store probably would have had to eat their cost, if they took them back, due to model/yearly revisions.)
P.S. I'm returning to just buying "decent" stuff from LL Bean. I seem to find less size variation in their products (e.g. jeans). And even "premium" products too often seem to be a crap shoot, these days.
Although I do love and baby my Asolo's, bought from an expert who spent an hour fitting me. Over a decade ago, now. But I'm not going to wear them out on daily tromps for exercise on our local gravel trail.
P.P.S. I also had a pair of those Chinese slippers -- looked exactly like the ones pictured. Bought somewhere in San Francisco's Chinatown. They were ok, certainly for the price, although I wouldn't run in them. Had them until I took them to a friend's, because they were obsessive about people removing their shoes. Never got them back. You can't trust your friends, either. ;-)