Does it look something like this?...
If it does then welcome to my world. I manage to do that to every pair of shoes or boots I own – particularly if they are material/mesh/lined but it still happens to a lesser extent on my work shoes (Doc Martens) which are unlined leather on the inside. I’ve come to the conclusion it’s not the footwear, it’s not even my feet, per se, but my gait – the way I walk.
I somehow flex my foot laterally inwards at the heel (rubbish description) as I walk. It’s particularly noticeable if I wear flip flops or walk barefoot on the beach.
I’ve tried the unlacing them properly to take them off/put them on. Nowt, no difference.
I’ve had my feet professionally measured to make sure I have the correct fitting footwear. Nope, not a jot of difference. Though I have corrected my over-pronation problem so some good came of that at least.
I’ve even tried those padded heel grips you stick in shoes…. Nope, they either just come unstuck and end up attached to my socks or wriggle their way out of the top.
Sorry I can’t be of more help and good luck with finding a solution - if you do find one, will you come back with an update so I can try it?
I just wanted to let you know you are not alone!