Using bonemeal on sea floor (sand, gravel) causes server freeze (no seagrass is produced) and moments later a connection lost / timeout error with the inability to rejoin (Connection refused: getsockopt) until server is restarted.

All plugins were removed with no change in behavior.
Using bonemeal to produce surface grass does not trigger the freeze.
Testing in single-player vanilla behaves as normal.

Prior to update from 1.21.4, behaved as normal.

Console event:

[18:21:52] [Server thread/INFO]: Sechesin joined the game [18:21:52] [Server thread/INFO]: Sechesin[/<ip removed>] logged in with entity id 41 at ([world]1279.9170473309769, 56.11774226365084, -658.6000842188198) [18:23:15] [Spigot Watchdog Thread/ERROR]: ------------------------------ [18:23:15] [Spigot Watchdog Thread/ERROR]: The server has stopped responding! This is (probably) not a Spigot bug. [18:23:15] [Spigot Watchdog Thread/ERROR]: If you see a plugin in the Server thread dump below, then please report it to that author [18:23:15] [Spigot Watchdog Thread/ERROR]: Especially if it looks like HTTP or MySQL operations are occurring [18:23:15] [Spigot Watchdog Thread/ERROR]: If you see a world save or edit, then it means you did far more than your server can handle at once [18:23:15] [Spigot Watchdog Thread/ERROR]: If this is the case, consider increasing timeout-time in spigot.yml but note that this will replace the crash with LARGE lag spikes [18:23:15] [Spigot Watchdog Thread/ERROR]: If you are unsure or still think this is a Spigot bug, please report to https://www.spigotmc.org/ [18:23:15] [Spigot Watchdog Thread/ERROR]: Be sure to include ALL relevant console errors and Minecraft crash reports [18:23:15] [Spigot Watchdog Thread/ERROR]: Spigot version: 4463-Spigot-b4e69d9-28229e3 (MC: 1.21.5) [18:23:15] [Spigot Watchdog Thread/ERROR]: ------------------------------ [18:23:15] [Spigot Watchdog Thread/ERROR]: Server thread dump (Look for plugins here before reporting to Spigot!): [18:23:15] [Spigot Watchdog Thread/ERROR]: ------------------------------ Skipped some lines of output