Hey,

as you just fixed SPIGOT-2297 have a look at the last 5 lines of ActivationRange
The code regularly accesses world.getChunkIfLoaded(...) which uses the aggressive version of the Chunk-Lookup: getLoadedChunkAt(...) in ChunkProviderServer (the one with the included "wasRecentlyUsed"-Boolean newly added to Chunks).

This should results in cancelled Chunk-Unloads in cases where entities are on that specific chunk.