Local Nests used to be Jynx and Scyther. Now, neither of them spawn any Pokemon consistently. Have the nests somehow been removed, or is it possible that region-locked Pokemon like Mr. Mime are messing these nests up?

My friend was talking about a park that spawned Scythers in his town, but became a null zone after a couple of weeks. Another friend mentioned how his local Jynx nest is now nothing. I looked at a Pokedex and noticed that 1-2 spots below Scyther and Jynx is Mr. Mime - a pokemon that would be regionally not allowed in North America. Does anyone know if it's possible that some nests, when they moved 1-2 spots down in the Pokedex, became Pokemon that couldn't spawn in their regions? Or is it just bad coincidence that these two friends lost their nests? Personally all the places that were nests in my area are still nests now - they just switched what pokemon they hold. If anyone else has stories of Scyther/Jynx nests seemingly disappearing, this would help explain what I'm thinking is the culprit.