Hello @Alzeldafighter, welcome to the forums!
Regarding the first issue, did you place him over a building piece, such as a ceiling or foundation? If so, have you tried to demolish the building pieces exactly below the position where you set him to guard?
For the second issue, did the Event Log message state that the thrall was killed while following you?
No problem @Alzeldafighter, it could happen to any of us.
Thralls may in fact die to fall damage, but when that occurs you do get a message in the Event Log stating they died, not referencing any source, which is likely what happened to the second thrall.
If you have no messages in the Event Log as it has happened with your first thrall, it’s possible that it returned to the previous guarding spot or that it somehow sunk into the map mesh or a building piece after setting it on guard.
We’ll be sure to forward this information and your feedback to the developers, apologies for the frustration the issue has caused.
To report exploits and undermeshing locations feel free to DM me or @Ignasis, and be sure to include screenshots or video of the location and undermesh base, thanks!
devtrackers.gg