Items outside activation range in water streams are lagging behind

Expected behavior

Items smoothly flowing around:

https://github.com/user-attachments/assets/a9fe4c23-087e-4bd9-bb0f-d9dadbbc063b

Observed/Actual behavior

Erratic motion of items in water streams:

https://github.com/user-attachments/assets/0793a296-21d3-4d6e-a63f-f79946be97fd

If I'm close enough they move normally.

Steps/models to reproduce

Boot up a new Paper server on Minecraft 1.21.4, build a simple circular water stream and move more than ~16 blocks away.

Plugin and Datapack List

plugins
[21:15:59 INFO]: ℹ Server Plugins (0):
datapack list
[21:16:24 INFO]: There are 3 data pack(s) enabled: [vanilla (built-in)], [file/bukkit (world)], [paper (built-in)]
[21:16:24 INFO]: There are no more data packs available

Paper version

version
[21:17:34 INFO]: Checking version, please wait...
[21:17:35 INFO]: This server is running Paper version 1.21.4-227-ver/1.21.4@7675321 (2025-04-28T19:07:04Z) (Implementing API version 1.21.4-R0.1-SNAPSHOT)
You are running the latest version

Other

No response

Reproduce the issue on Paper 1.21.4-227 using a circular water stream, with no plugins or extra datapacks, and compare item motion within and beyond roughly 16 blocks. Trace the activation-range handling for item entities and verify that items continue moving smoothly when the player is farther away; add or run a regression check covering both distances.