Ask HN: Anyone else have long-standing GMail filters that have stopped working?

Some filters I've had working in Gmail for years seem to have intermittently stopped working over the last year or so. I'll have a filter with a simple subject line match, and now I'm getting these messages in my Inbox, when they should be bypassing it.

Haven't been able to discern any pattern to this yet, but I haven't really dug into it. I wonder why the regression? Is this some kind of throttling? Like approximate matching?