We recently received the new HP 8460 G6 which has a Western Digital PC SN520 NVMe SSD hard drive. We experienced the same problems where the imaging process with partclone was SUPER slow <10MB/min. This same fog installation had no issue with the HP 840 G5 with a Samsung SSD hard drive.
I first tried the experimental init.xz that @Quazz recommended but it failed with a kernel panic.
I then upgraded fog to the latest dev-branch and re-tried the init_partclone.xz that @Quazz recommended.
That solved the issue, I’m imaging the G6 laptop at 1.31GB/min.
Thank you for solving my problem @Quazz.

jpd