Sigh. I really do proofread and have multiple people proofread for me as well, but sometimes things fall through the cracks.
On the key for colour #17, it shows a filled star as the symbol, on the chart it is two dots side by side. For colour #18, it shows two dots side by side, on the chart it is a 2.
They have been corrected and the correct version is now in the Etsy shop and with my distributors so it will be correct in future orders, and only in the specialty stitch version - the cross stitch only one is correct.
I feel completely awful about this and I'll make sure I check even more in future. Thank you to Barb who notified me.