XPS 15 9560, Dell Repair Mistake

Posting for XPS 15 9560

After a plethora of issues I sent my laptop in to have the SSD replaced (it is still under warranty, this was no issue). When it returned, the battery life was dropping faster than normal, and power would randomly get cut off even when plugged in. I was told it was most likely the battery and that it would ultimately cost $140+ to send if off and a) diagnose it and b) replace the battery, since it is a "consumable part".

I decided to open the laptop myself to make sure all the connections to the battery were snug, which they were. However, one of the screws for the SSD mount (not in use, my model has M.2) was LOOSE and happened to be attached to the back cover magnet at the time I opened it up. After putting the screw in its rightful place, I have had no issues. Clearly this was causing some sort of short, and I have a sneaking suspicion it has RAPIDLY decreased the life of my battery (currently at 24% life since the repair).

Has anyone else had any issues with repairs? Is there any way to go about filing a complaint?