Yeah this is my life, I'm 38-40 waist depending if I've been looking after myself.
Basically that size doesn't exist on the high street, and it's never in stock online. I literally have to buy summer clothes in winter and vice versa because that's the only time I stand a chance of getting it in my size. I've wanted to buy a new pair of shorts from Levi's all summer and despite checking every week, I've not seen any in stock once.
And that's all before it arrives and then all the shit you mentioned can happen.
Tbh that's part of the reasons I want Levi's ones specifically, they have been very consistent with sizing in my experience