Most likely in this situation the processor configured with output pins in high impedance mode, and leaving the outputs in an undefined state may causes this problems, so it is recommended to tie the MOSFET load switch input to GND. The external pull-down resistors, if provided, should block the load switch for the inactive state at the microcontroller output. The value of the pull-down resistor should be chosen such that not to increase the output current, usually a 10k up to 100k resistor can be used for.