I already had this problem long before the patch, so I guess it got nothing to do with steam but is in fact some client-based problem in dealing with hardware.
All 3 of my controllers have different amounts of the same issues, but no issues whatsoever on any other computer game.
That’s “partial” controller support for you 
Coming here to say that uncheck the “Controller Vibration” option in the settings solved my problem and for another people too. Thats why when i put an old version of the hotkey files worked, because it didn’t have this option checked.
Adding my hat the pile. Toggling controller vibration fixed it for me.
Along with Calibration, another option from google that worked for me was changing controller deadzone crom Cross to Square. Credits goes to a person from Klaipeda shout but I forgot their name D:
TL;DR:
Make Steam detect and setup your controller by enabling it on Controller Settings. For generic controllers you should map the buttons before next step.
Find the Joystick settings and change its Deadzone from Cross to Square.
If you have swapped buttons (like O being swapped with X etc) you can also open Big Picture mode and ToS -> manage game, then edit it there instead of in the hotkey_joystick.xml file. It should be easier and the buttons won’t be swapped back after a maintenance or anything.
A better guide on how to change the joystick’s deadzone into Square:
https://www.reddit.com/r/RocketLeague/comments/6h8nm6/tip_you_can_increase_your_controllers_diagonal
also had the same problem, when I took the option of vibration the control returned to work quiet again.