AntiGhost
AntiGhost is a Client Mod that allows the user to fix invisible "ghost blocks" without needing to relog. It requires the Forge Modloader, although Fabric ports are available for later versions of the game.
What are Ghost Blocks?
Ghost blocks are blocks that seem to be air to the client, but are solid to the server. They occur when the server and client are out of sync -- the client sends block break events to the server, but the server either does not get them or rejects them (can happen if the client thinks the player has Haste but the server does not), so the server does not break the blocks. The client now thinks the blocks are air, but when the player tries moving into those blocks, the server kicks them back.
How does AntiGhost work?
AntiGhost requests the server to resend all blocks around the player within a 4 block radius cube, thus making relogging unnecessary.
The player triggers this with the default hotkey G, or with command "/ghost".
Trivia
When using AntiGhost, you are incapable of writing a chat message that begins with the characters "ghost " (all lowercase, followed by a space). This is presumed to be an "easter egg".