When I work in 3D Max i regularly have this problem.
CPU Usage drops from 100% to 0% and on the same time Disk Usage rise up from 0% to 100% for ~30sec.
It happens every 5 - 10 min.
Also can happen when CPU Usage is low, but Disk Usage rise up to 100% and everything is freeze until Disk usage normalize.
2 days ago this SSD Disk worked fine with the previous cpu.
Tried chkdsk.exe, everything is fine.
Tried disconnect the HDD.
Motherboard ASUS PRIME X399-A
Latest BIOS version
And what does Resource Monitor say is using all that disk activity?