What was the most frustrating part of your last local fine-tune?

I’m working on a local fine-tuning tool, and I’m curious where people actually lose the most time.

Was it getting the environment working, preparing the dataset, fitting everything into VRAM, or getting the exported model to behave like it did during testing?

Or did training finish successfully, but the model barely improved?

What model and GPU were you using, and what finally solved the problem or made you abandon it?