The investor at the center of the pandemic meme stock craze said Friday that he still believes GameStop’s management team can turn the struggling video game retailer around.

But remarks from the man known on social media platforms as “Roaring Kitty,” made during a live stream on YouTube that drew more than 600,000 views, didn’t keep shares in the company from plunging about 40% — a warning on the unpredictability of meme stocks.