Information

Minecraft version: 1.19.2
Modloader: Fabric
Fabric loader version: 0.15.3
Environment: Singleplayer+Multiplayer

Mod name: World Border
Mod version: worldborder-1.19.2-4.3

Description

So the borders work, warning appears (maybe a config for how far back the warning appears would be nice) when I hit the border it loops me perfectly. The issue is I appear at the coordinates, both looped and ten blocks back inside, but the Y coordinates essentially rise to over 1000 and survival players die on impact with the ground.

Were you in the nether dim?

I came to report the same thing. On 1.21 Fabric server, nether tp occasionally tps the player to world height.
Upon closer inspection, this occurs when there were no avaliable locations below bedrock (aka a solid column of netherrack).

If this is a separate issue, I will make a new issue report.