This has been happening to our order numbers since the beginning of the year, it’s rather irritating to constantly fix Excel column formats, we also see it in Epicor itself in some financial year fields.
Epicor does helpful formatting things when you export-to-Excel. The way around that is right-click > copy all with headers, then paste into Excel. Sometimes it works better to paste-values-only (alt-control-v), and it doesn’t hurt anything so that’s a useful default habit.
I usually use copy all with headers and then ctrl v which results in salesorder numbers with commas, just tried alt-ctrl-v and unfortunately same result.
Leading. zeros is a big pain too, apparently there is a new feature in Excel that will allow this, include leading zeros. Not sure if this is fully rolled out yet.