Mmcqd and Xorg eating CPU

Hi all,

I’ve just received a DragonBoard 410c, Amazon version, so it had Debian installed by default. I did a dist-upgrade just by reflex, as the very first command. This might or might not be relevant.
The problem is that whenever I boot, mmcqd generates a load of ~2 with >50% CPU usage, for a couple of minutes. Sometimes it’s 2, but now it’s been that way for 10 minutes now.
Xorg uses less CPU, about ~10%, which would be (relatively) OK, but sometimes it goes up to ~25%, and X hangs for about 10-12 seconds each time.
Has anyone seen anything similar before? Did I screw up by doing a dist-upgrade?

Thanks in advance,