If drones part of a fleet are set to "sentry mode" (while still docked to the ship) and are launched via launch-rails in the presence of an enemy, they will instantly stop and re-orient towards the enemy.
Basically, they stop and orient instantly after undocking, no matter their thrust value. This was done with drones that had 1:1 thrust/mass ratio, so there's no way that they could go from 25 m/s to 0 in half a second.
This is pretty problematic. First off, it increases the chance of the drones colliding with the carrier, since they're not pushed away properly by the launch rails. Secondly, if you have more than one drone coming out from a single launch rail they'll all collide with the first drone and cause a massive traffic jam. This in turn can cause drones to REDOCK to the carrier, messing up pickup-point assignments and the entire launch in the process. In essense, you're forced to keep the fleet on idle, and can only turn on sentry mode after all the drones are launched (and this is mid-combat). On idle they just glide normally away.
Normally, the drones should simply glide away at 25m/s and reposition themselves at the speed their thrust allows.
How to recreate:
1) Build/get a carrier that can launch drones with launch rails
2) Set the fleet to sentry mode or or any mode that turns on the combat AI.
3) Spawn an enemy
4) Launch the drones
5) Watch the collision clusterf*** that ensues.