Looks like the P8 problem is one introduced in the 4.15.0-22 release (which was the security update related to spectre v4). There is a fix pending for that and will be included in the next cycle. So given this is not a regression introduced by the kernel from this current cycle, I would switch regression testing to good and we need to make sure to verify that the next cycles kernel does work on P8 (maybe deploy xenial and replace kernel).
Looks like the P8 problem is one introduced in the 4.15.0-22 release (which was the security update related to spectre v4). There is a fix pending for that and will be included in the next cycle. So given this is not a regression introduced by the kernel from this current cycle, I would switch regression testing to good and we need to make sure to verify that the next cycles kernel does work on P8 (maybe deploy xenial and replace kernel).