If you look at the video, you'll see that I demonstrate that the only variable that makes a difference is the vertical position. The slimes didn't spawn when the roses were not there.
Has this been looked at, yet?
Fix worked. I used NBTExplorer and looked at the region with chunk 113, 202. There were many entries for TileTicks. I deleted these, restarted the server, broke and re-added the problematic blocks, and both dropper and torch functioned correctly. Thanks for your help.
Link to zipped world files has been added above.
https://drive.google.com/open?id=1LGwA6msSR7c0YLnQuycwChUylCRIx99J
Yes, this came from the wiki. Can you please supply the correct y values at which slimes will spawn?