OpenBSD hangs in X, but mouse can still move (ThinkPad T470)

I've been using OpenBSD on a ThinkPad T470 for a couple of days now,
and the experience is very nice. However, I've noticed an issue that
occurred twice today: while I'm using cwm and a bunch of apps (Firefox,
Claws Mail, KeepassXC, xterm, nothing special), OpenBSD completely
freezes, but the mouse cursor retains