Very common unfortunately... The vinyl is acting like a knife (or a letter opener) on the edges during transportation (when moving against the sleeve paperboard). This is the result.
This is why very professional sellers will send you the LP with the vinyl OUTSIDE the sleeve (and when there is an inner sleeve, with the vinyl in a plain sleeve, otherwise the same thing happens to the inner sleeve obviously...). Now of course this is a problem if you want to get your LP "sealed".
I do have to say I don't often see that happen with sealed LPs. Good packing does seem to help - i.e. crappliy repackaged ones ordered through my UK forwarder seem to have generally gotten it the worst.