It is a good idea to do some minor maintenance on the microswitch in the Cali sink tap. This is a step by step guide. Also contains link to video showing the internal working of the switch.
Great guide thanks. Sorted my T5.1 tap issue out with these instructions. Fiddly to get the c shaped clip back on. I found with tweezers, securing the right hand side first then pushing the left side into place with my little finger worked best.