So the initial problem was with the RAT probe?
It has not been explained with an all out technical precission, but it has been reassurred as some "not important, minor issue" involving the RAT probe, believed to be either a sensor or a ice-protection heating device failure related to this probe.
It wasn't clear from reports what had been disconnected (tripped-off ... technician spokeperson speaks of fuse taken out) but in all likehood it was the ice-protection heating device and not the RAT probe itself.
Whatever it was, seems clear it was some minor glitch and that both the pilot and the technician clearly understood the limitations of their actions and felt confident on the flyability of the plane without issues.
Wheather in Madrid was fairly hot at the time (around 30ºC), which with the sea level at Barajas would've called for air density on the low side of things.