The one thing I noticed making differences—and I want to emphasize that this was slightly BEFORE the so-called "Vicinity rollback"—was services. I first saw an explicit instance on March 21.Some of the competitors I monitor also took a hit. That combined with my client increases leads me to believe there was another update or Vicinity is being rolled back a bit.
Yes, I know, it's never been the case before, but I've had several instances recently where I adjusted services and this seemed to have significant effect within a few days. It seems to be especially the case for keywords that do not appear straight up in the category name. It's the only explanation I can think of that so many clients we'd been having long term trouble with (as in, before December 2021) are suddenly starting to rank: we have always been very diligent with using services and this seems to be rewarding us as generally not that many profiles take advantage of services.
Now keep in mind that I handle mostly French-language material, so that may be relevant. What I've seen is significant moving of the needle on long-tail keywords. Especially noticeable for anything that's not straight up in the category name already. I have not done A/B testing (for complicated reasons we don't have the resources to actually do it), but I've seen with my eyes enough anecdotal cases that I'd say I'm at around 85% certain this is in effect as far as French-language searches in Quebec go.