Wage reporting when hours change weekly after 10 years as a mechanic

I work some days through a staffing agency while still certifying. Thank you in advance. Sometimes my paycheck is late by a week. Who can I ask without risking my claim?

Thanks for writing this out. I went through something close to it 5 months ago, and it settled down once I kept a simple log of every call and form.

The claimant handbook has worked examples for part-time pay. Mine was clearer than the phone line.