are you asking about conditionals on fields inside tabs (there is a problem with fields that are in inactive-hidden tabs as far as I'm aware, at least it was some time ago) or on the tab fields themselves ?
looks like my statement about the bug is base don outdated information, I just tested this and everything works as it supposed to regarding fields inside tabs on Seblod 3.8.2 and Joomla 3.5.1
So I presume, this must be something on your setup, most likely there is some javascript error, please check for those first.