Simple.

Don't use Sendle. Especially as they are a broker NOT a courier.

Or any courier, frankly, unless your items are too big for AP.

eBay shipping options (from memory - I stopped using eBay labels when they stopped passing on the massive discounts their volume would get from AP) have several options. Just because Sendle is the first one doesn't mean you have to use it. Except that it is, on the surface, cheaper. But not, as you have found.