I've filed a bug report with Eset, though those reports - that take the form of support tickets - are not externally accessible.
OK, so with the help of Deleaker, I've easily identified the main culprit: Beyond Compare. After blocking its two extensions (normal + UWP), everything seems to be quiet and peaceful — no more spikes of handles. I’ll keep an eye on it over the next few days.
What's strange is that, considering the popularity of BC among DOpus users, this issue doesn’t seem to be widespread 
Maybe there's something more to it?