When player connects to the server, and the location where the player will spawn is has a single solid block with air below (such as elevated block), the player will briefly fall around or through the block (visually), then the correct position will be set. (on Spigot, if falls directly through the block, whereas on vanilla it seems to avoid the top block.)

The issue occurs in Multi-player 1.8.x when connecting to Vanilla 1.8.0 and Vanilla 1.8.8 builds.

This issue was not reproduced on single player 1.8.8 Minecraft client.

Issue forwarded from Spigot JIRA [SPIGOT-1081