ttsesm:

I didn’t understand that part clearly, where and when I should apply this transformation. You also suggested it in one of your previous messages. Should I apply this before I get the error between my targets and the regressed values in my loss function or elsewhere


Yes, you change targets, so that their distribution is more similar to uniform. Actually, uniformity is also one of the reasons to use per-cluster regression for inhomogeneous targets (like you tried above IIUC)