My REGA ISIS Valve cdp took over 350-400+ hours (lost count) in a continuing non-linear series of performance changes and intermittent plateaus before I could finally say it was as smooth as ice over glass.
IMO for sure, just a nominal couple of days and maybe even up to a minimal 100 hours of break-in time won’t cut it to permit the spinner to settle in.
..., patience, patience ....
postscript
independent of of the above, try warming up the whole system first by turning it on for a couple of hours first before you crank it up. Do I find a noticeable difference in taming any "edge" / sibilance / harshness blah blah by doing so .....in my system, yes.
+1 on the prior post re: swap-out of any crap stock power cord and a swap-in if a better quality build one. Experiment with them to weed out the contenders from the pretended... They all have their sonic signature .