Strange chunk loading shapes

[GreenlandFan1]

Ever since the update to 1.21, newly generated chunks load on the map in strange patterns ('badloading.png') rather than loading smoothly ('smoothloading.png'). Note that this is purely a visual bug with the map; no effects on chunk loading are observed in-game, and the chunks that are not loaded on the map seem to be loaded in-game.

[jpenilla]

Usually patterns like these come from mangled world data that was generated before squaremap was installed. I need more information to do anything with this, for starters what mod/plugin loader this is on & any related errors. Ideally reproduction steps from a fresh server as well.

[GreenlandFan1]

We're running on 1.21 Paper Build 91 (the latest one) with the standard Fabric server-side performance mods (Lithium/Krypton/FerriteCore/etc.) and is happening to everyone regardless of whether or not they are running client-side mods. The issue only seems to be happening with chunks we've generated since updating the server to 1.21 from 1.20.4 a couple weeks ago; prior to updating, we had no issues with the map loading in the way presented in my first message. A friend of mine runs the server, so when they get back from work, I can work with them to attempt to reproduce the issue.