Had Evohome running for under a year with 12 HR80UK's and am getting an unusual error message, it comes up to the right of the temperature setting as follows:

Normal 21C
With error 21C then two horizontal parallel lines the wide of one character, one at the top and one at the bottom?

Does anyone have any ideas what this means?

The Radiator involved is unable to go above 21.5 C no matter what the set point is (even full) and I am wondering if it is a reduced actuator travel? Don’t know why and don’t want it and ideas how to fix it appreciated. All the other rads are fine, as has this one for a while.