Memrise is forgetting that I've learned words

I’ve started seeing this bug in Memrise in the past couple months where I’ll learn some words, then come back a few days later and it presents the same words again. These are not reviews – it’s actually presenting the definitions again.

In fact, if I look at Level 3 - 151 - 225 - Introductory Spanish 1 - Memrise right now, I can see a bunch of words listed as “ready to learn”/seeds that I know for a fact Memrise has already introduced in learning sessions.

It’s very frustrating. Anyone else encountering this?