I regularly get SMBD processes that keep eating up 100% cpu, even under barely any load. After a reboot they disappear, only to come back half a day later.
Today I found two processes stuck at 100%, so it is not limited to one process.
Once a process hits 100% I find there is a significant slowdown in file access / read / write times.
As reccommended by https://www.ixsystems.com/community/threads/1-smbd-thread-stuck-at-100-cpu.87728/ I generated a core file (using gcore, as kill -6 did not seem to work). It is attached to this issue.