I improved sync script - now it will ignore games unavailable (do not have product card) on Steam store.
@p4n0s In your case it looks like it fixed issue completely: last sync removed 19 games from your wishlist.
However in other cases this may be more tricky. Some games on Steam are still available (they have product page), but they're hidden from search, and this affects wishlists to. For example Rocket League has product card, but it is hidden form searches, so normally you can't find this game on Steam. If you find this product card and click "Add to your wishlist" button, it will not appear on list of wishlisted games on Steam (because it is hidden), but it is still there in API and GG.deals will sync this game and show Rocket League on your GG.deals wishlist. The only way to to fix this is to find product card on Steam and remove game from wishlist there. AFAIK it also affects region locks - game can be hidden in specific regions and it may be hidden from your wishlist if it is linked to one of these "banned" regions.