This has been happening on both PC and mobile (android) for a couple months.
I have an exclamation mark (notification) on the shop of new items, and when I open the shop, it shows the exclamation mark on the Battlegrounds tab. When I click (or press) to go to the Battlegrounds tab, there are no new items shown.
Sometimes when I exit the shop, the exclamation mark will clear (not always), but it ALWAYS reappears every time I open the game, despite NO new stuff in that area of the shop every time I check.