I just received feedback from support/technical team. I cannot test it for now but posting below the answer in case it may help someone else.
"The problem with the touch switch can occur when the circuit board 137-09 is fitted the wrong way round. The ‘switch’ is dependent on the spring on the reverse side being in contact with the touch plate 137-07. Although the board may look symmetrical it matters which way round it is fitted; the spring isn’t fully in contact with the touch plate.Consequently, try fitting board 137-09 the other way round."