Hello
Its quick fix post for future players to avoid a rogue class characters removal.
Bug looks like this:
When you finish class quest for rouge [24] LVL with cure for 7 days-long poison The Touch of Zanzil you may want to train your lockpicking skill a bit higher.
With doing so on Westfall chest you get that stupid poison again - what happens is game doesn't allow you to use stealth skill.
In my case - sollution was: to use pose included item [ like a tavern chair] and use a stealth from that position.
Hope you get that lucky because high lvl rogue with Stealth ability disabled is pretty much useless.