It seems that between 4.21 and 4.22 something changed in how tilesets are rendered.
I’ve compared tilesets between version 4.22 and 4.21 of my game and some of the larger tilesets really degrade performance. See attachments:
This is 4.21
This is 4.22
Other rooms with the same size give different results, but I noticed a single value that might explain what’s happening: when viewing the tileset in the editor, the “Render Geometry → Sections” value seems to be related to the fps loss. Triangle count seems mostly non-influential.
Compare these two tilesets with equal size and similar triangle count, but completely different section count. The first one doesn’t affect the framerate at all, while the second one (the same tileset from the first two screenshots) causes a heavy drop.
The tilesets have not been modified between 4.21 and 4.22. This is purely a rendering issue, I believe.