No members here can do anything about it.  Ebay do not read Member to Member forums.

If you have proof, you could try and speak to Ebay about it.

Proof?

Can you share one of the item numbers so we can look at the seller?

A few years ago I was in an op shop which had an upstairs section.

It had recently been turned in to their eBay section, in which items were listed on eBay, but could still be bought in person.

Perhaps that is what is happening and, while annoying to the bidders, is something that can happen with private sellers also, who might sell something through social media (as an example), and then have to cancel their eBay listing.

As far as I know, it's not against the rules to list items on eBay that are for sale elsewhere (someone please correct me if I'm wrong).