Sounds like the flap follower cable inner and outer is worn out,
Can be purchased in the states for about $1 dollar a foot.
Go for the steal outer rather than plastic, brakes up.
We have a 177 had to replace it but maintainer purchased from Cessna at £300 pounds
The gated selector has a couple of micro switches and needs the follower cable working Ok. Best to replace cable.
One idea in the states is use a larger diameter outer with a Teflon (ptfe) lining, from motor cycle tecnology.
Another low tec idea is paint some lines on the port flap and wing so as they move back and down they indicate position.