We recommend to work with this small checklist for us solving your problems quickly:

1. Optical check (photos of the product, top and bottom side, in focus, close up)

    A short Video to show what is not working could be helpful.

    Is the product new? How is the soldering? Are components missing?

2. For ESC: FETtec Configurator telemetry tab check (failure messages? Which firmware is installed?)
    For FC: KISS GUI check (failure messages? Which firmware is installed?) 

3. Setup
    FETtec ESC and FETtec FC or other combinations?
    Newest firmware installed?
    Cap installed? (FETtec Spike Absorber installed?)
    Motors optically ok? (Check KV and Lipo combination) 
    No screws touching the windings?
    Props ok and not loose mounted

If you need our help after working with this checklist, give us as much information as possible about your quad with your email to service@fettec.net