I notice this happening on our private/rented server. LEVIATHAN’s Children.
The map is SIptah.
We do not use any mods.
In this case:
All thrall fighters were stationed on ground level foundations made of T3 Reinforced Stone.
We have roughly 12 fighters stationed near the main gate with each one standing on their own foundation (all foundations are connected).
One way we pulled this trick off was by placing doorways on foundations and positioning a fighter at each doorway, then remove the doorway.
Another way was by using columns stacked 3 high with a ceiling panel on top, then placing the fighter on that ceiling, then dismantle the first column (to dismantle the column assembly) to allow the fighter to drop down into position on the foundation adjacent to the next fighter.
Observation:
It happens at intervals that seem to be regular intervals roughly between 5-10 seconds. (hint: Inconsistent timing indicates other demands going on at the same time).
Like a sweeping motion, they drop through the foundations to the ground then a few seconds later recover to their original positions.
Some, occasionally stuck in the foundation they were standing on and cannot move. We were however able to reposition them successfully without the need to dismantle the foundation. However, due to constraints of the activity going on at the gate, those who had to be repositioned were placed just out of range of their “team-mates” until the activity ended.
This is a physics glitch related to position/location polling.
This appears consistent with the addition of being able to place thralls on benches and seating arrangements as well as on “station” positions.