I placed down a ton of infested blocks, but some of them have become un-infested and returned to normal stone bricks, cobblestone, etc. This has happened in other worlds before.

Steps to reproduce this bug could be:

1. Place down a bunch of silverfish infested blocks
2. Wait for a while but stay in the same chunks
3. Use pick block, /detectblock, or other methods to see if the blocks are still infested
4. Some blocks should be not infested anymore due to this bug