Sebo x4 auto.

Hi.
I have one of these vacs that illuminates bag full/clog light and shuts down after a few seconds.
There is no blockage and the bag is new.
I suspect the control pcb part no NPPTSTXSNM-3 is faulty.
This is a later X4 Auto with a 1100W motor.
The earlier models fitted with a control pcb part no NPPSTXSM-2 you could manually reset to solve this issue by adjusting a variable potentiometer on the board.
Apparently the later pcb’s can only be reset with a “special tool”!
A new pcb costs about £78.00 which seems a tad expensive for such a simple board.
Apparently another alternative is to replace both the power supply and control pcb’s with the earlier version recycled parts.
Any information regarding the “special tool” would be helpful and I’m just a bit curious as to how the pcb detects a bag full/ clog situation?
Thanks in advance.

Noel