This is not a problem to fix but it does require opening up the unit and doing a bit of dis-assembly work. There are 4 screws in the bottom of the unit. Make note that the longer screws go to the rear of the unit when you re-assemble. The top shell will lift off but is connected to the power and heat selector switches so just angle the top out of the way.
By holding down the "release" lever in the rear of the unit you can rotate the rollers backwards to recover the end of the foil in order to pull it out. If this doesn't work the next step would be to remove the two screws holding the motor/geartrain in place. This will allow full access to the rollers to rotate so you can use both hands to get into deeper to find the foil and remove it.
Normally this should never happen however if you do not get enough foil wrapped around the leading edge of the PCB (normally 2" is good) this is when the foil might slip out from under the board and get stuck on a roller. If you notice that the board is coming out without the foil, this is when you should cut the power to the unit, hold down the "release" lever and pull the board and foil all the way back out.