"In the design plans for the system, the word 'main' was used inconsistently between the device that sends the electric signals, and the device that receives the signals," NASA said in a written statement. "On the signal side, 'main' meant the main parachute. In contrast, on the receiver side 'main' was used as a reference to a pyrotechnic that fires to release the parachute canister cover and deploy the drogue.
"Engineers connected the two mains, causing the parachute deployment actions to occur out of order," NASA said.
I used to work as a technical writer and I always got shat on by engineers who worked along the lines of "real men don't write documentation". But those guys won't read this because reading is just too hard for them.
It always fascinated me how, something apparently as simple as a parachute, is so hard to do well. We can operate a fucking drone flying repeatedly on the surface of other planet but we struggle to open a piece of cloth.