Abominable Snowman.2036

Same problem here, for me Bloodtide Coast #4 and Sparkfly Fen #2 do not appear.

What you could do is retrieve all of the achievements from the API, and create a mapping from name to ID that way. You can start with https://api.guildwars2.com/v2/achievements?page=1, and then either use the x-page-total header or use the next URL in the link header.