This seems like thermal throttling. Threadripper CPUs are demanding to cool.
Also, 40-45% indicated load is close to the 16 threads your license is for. The Windows scheduler loads physical cores before virtual cores to increase perf. Hyper-threading cores only add about 10% performance.
@The Imp: DDR4-3000 is probably and XMP profile on the RAM. 2133 is the baseline JEDEC profile. Early Zen systems were pretty picky about RAM to run faster than base JEDEC speed. Firmware updates helped with this quite a bit over time. If this system is running an older BIOS updating that could help. Zen based CPU performance is more impacted by RAM speed than most because the Infinity Fabric speed linking between CCX modules is based on RAM speed. DDR4-3200 has been the sweet spot in the testing I've seen.
@Clanty: Please provide more info on your system. Is this a major manufacturer system (Dell, HP, Lenovo), a whitebox (local computer shop or smaller online builder) or a self build?
Speccy or HWInfo should be able to provide more system info and temps for you to post in the thread. Getting your firmware current and confirming adequate power and cooling are the best next steps.
https://lifehacker.com/speccy-gives-...hardwa-5401456
https://lifehacker.com/hwinfo-provid...you-1044830886