I've been using the OptimizeExpression function again recently, and cleaning up the results by hand. Its results have been unbelievably sub-optimal in my recent usage, as opposed to the past. So much so that it doesn't even require manipulation of the results to see.

Have any of you run into this recently? Can you test this on older versions?

For context I'm in Mathematica Online, so I'm using version 12.0.0 for Linux x86 (64-bit) (March 31, 2019). I don't use the desktop version.

f[u1@P]+c f[u2@P]/.f@u_->3/2/u(1/2/u-1/Tan[2u])//FullSimplify
{%,%/D[%,P]}/.{u1->(j1 Sqrt@#&),u2->(j2 Sqrt@#&)}//FullSimplify
Experimental`OptimizeExpression[%,OptimizationSymbol->a]