lewis02 :
1.5 volts is quite high. I got mine to 3.9 @ 1.325v. I'm pretty sure the maximum safe voltage for ryzen 5 is 1.425, so you should probably lower it.
Use programs like cpu-z or even task manager to check your cpu performance while under load. If it's noticeably lower than it should be you may have caused some damage, or might even have a faulty chip.
Is your chip stable at that voltage? I have a 1500X as well, and I just tried running Cinebench with the OC at 3.9 and 1.35 volts, and it crashed. I have an Arctic Freezer 33 eSports One with a custom fan curve that keeps the CPU under 60 degrees while running Prime95 with an OC of 3.8 @1.31875v, so heat isn't the problem. I know the silicon lottery is a huge gamble with any Ryzen chip, but I don't think 1.325v is enough voltage to maintain an OC of 3.9 when stressing the CPU.