I had noticed this issue before in SCP: Roleplay but was not fully aware of what the cause is. Today, we activated the Improved ModelStreamingBehavior in Glacier and it has caused the same problems we face in SCP: Roleplay.
Characters will seemingly have broken motors resulting in broken animations and/or clipping through the floor upon spawning in. Teleporting does not fix this problem.
This error, for example, becomes very frequent upon enabling Improved mode:
I do not have reproduction steps unfortunately, but by simply playing SCP: Roleplay you should be able to encounter this problem.