Information

Minecraft version: 1.21.1
Modloader: Fabric
Environment: Server

Mod name: Tree Harvester
Mod version: 9.1

Description

At random times, the mod stop working. When trying to chop down a tree, the block will break only to reappear and break again. Only the targeted block breaks. There is no indication that the server is overloaded or any other apparent issue. Deleting the config and restarting previously fixed the issue.
Other mods on the server are:
Advanced Backups 1.21 3.6.3;
c2me 0.3.0 alpha 0.204;
Collective 1.21.1 7.84;
Double Doors 1.21.1 5.9;
Fabric API 1.21.1 0.301.0;
Ferrite Core 1.21.1 7.0.0;
Universal Graves 1.21.1 3.4.4;
Krypton 1.21.1 0.2.8;
Lithium 1.21.1 0.13.0;
ModernFix 1.21.1 5.19.3;
Slumber 1.21.1 1.2.0;
Unloaded Activity 1.21.1 0.6.4
Double Doors and Unloaded Activity were not present when the issue first occurred.

It turns out, that if you don't crouch for long enough after breaking a base of a tree then the mod doesn't work. Staying crouched until the tree disappears has consistently fixed the issue.