From my experience this occurs only if your loot discipline is set to anything but "current discipline". I've trashed 3-4 thyrsian crates before i read this in another thread (it was about nobble decurion crates but it worked for thyrsian as well).
EDIT: Forget about it, last time it was a fluke, next thyrsian crate got destroyed while loot discipline was set to "current".
PS: Bioware, pls fix this mess.