Local Switch Test
This is Google testing SERPs with inclusion or exclusion of localized results to experiment with market response.
Does the market favor search results with local links?
Or would the CTR improve with international results on page 1 instead?
It’s hard to say if this is purely because of automated changes in the algorithm or if it is in fact a Google split test of some sort. But it’s possible for the local knowledge-graph box to appear one day for a certain keyword search and then disappear the next day for the same search, same user, same location.
You have little power over this feature unless you can identify which keyword phrases are triggering what type of SERP response and optimize with a bias one way or the other.
This is a tricky and time-consuming process, but can help your site gain market exposure to either mach larger national or global audiences, or much more focused local audiences.