REI plugins reload in two stages, START and END.

On Client, START stage is called when the client receives a recipe sync packet from the server. END stage is then called when the client finishes processing the recipe sync packet.

On Server, START and END stages are called when the server finishes data pack reload.

Plugins may listen to the different stages via preStage and postStage methods, please note that there are multiple Plugin Manager instances.

You may trigger a full plugin reload in REI in Config > Advanced > Reload Plugins or executing /reload.