There is most likely an error with the configuration code you add for the 4th signal.
Instead of using Pins tool and adding the extra code manually, I recommend you to use the Peripherals tool, under ConfigTools, to set up the configuration of the PWM module as a whole with all of the signals you require. You should be able to do the setup of each submodule in a more straightforward manner, and make sure the setup of each submodule is the same. Here I added all 4 submodules by simply clicking the "+" button beside the "Submodules" section, and set up each as PWM.

BR,
Edwin.