Sorry for late reply.

To explain: My first y axis setup did have 3x 15mm rails and the leadscrew in the middle of the rails. No issues. Then i redesigned the z axis so i could fit my bt30 spindle there. Two 15mm rails stayed there and i removed the third rail and in addition i relocated the leadscrew. Now the leadscrew is not in the middle of the rails but on top. This 2 modifications caused the rails to wear faster since only 2 rails left and the leadscrew on top made additional leverage on z axis. Machine works 8h/day all week, half of the time the 2.2kw spindle is on the limit. After changing top rail with the spare one, the error was gone.

I am changing the design again. I am getting 2x rexroth 25mm rails for y-axis and placing leadscrew in the middle and hope there is enough room left for the big hsk63 servospindle.