A lot of things could be the issue. The first thing I would do is disconnect the joysticks, one at a time, and also (if possible) try another monitor. If you are using a mouse and/or keyboard and didn't mention them, try disconnecting them and/or replacing them with different ones. If any of these manoeuvres causes the problem to go away, you probably have your culprit. If not, you have to consider the possibility that either the Pi or its power supply is defective. BTW, there is no such thing an an "official charger". The approved device that plugs into the power port of the Pi is a Power Supply. It is because other devices are, in fact, designed for use as chargers that they cause so many problems when used to supply power to Pis.