High System Load with Multiple Snaps

I’m on Ubuntu Mate 22.04 (Jellyfish), and am seeing issues when running multiple snaps (typically Thunderbird + one other). The system load goes up to over 25, and the system becomes completely unresponsive. If I can afford to wait, it sometimes resolves but can take 40 mins or so.

If I have htop open when it happens, I can see that all the CPU load seems to come from multiple threads from every snap running - I am looking at it right now, and the system load has risen to over 30 as I have written this, and all the load is from the Thunderbird and Slack snaps. This never happens with only Thunderbird open - it’s usually Thunderbird plus one other snap, and the load from the snaps goes up together, even when all the apps are idle.

I have no idea how to troubleshoot this - are there any diagnostics I can run to get some insight into where this load comes from? I’d rather not have to nuke these snaps and reverts to APT installs, but my desktop is unusable when this happens.