If you dig into the game's insides on a coding level, there are a lot of flags and so called "points". SH especially has a bunch of those, which can permanently glitch out. Every other patch I've personally played, there's a new SH problem.

(One example: if her wound scene played outside a scene, EVEN ONCE, as background party commentary, she would at some point permanently stop gaining a point type. At another she would ALWAYS accuse to player of not respecting her decision in regards to the Nightsong).

The game is complex in the sense that the code is spaghetti, the flags are meatballs, and the smallest error has far reaching consequences. At some point, very early into release, it was impossible to break up with some characters I think, and those characters weren't even romanced. There were a lot of complaints. It might not feel complex to play for someone personally, but the coding is mess of gigantic branching trees of choices.

Some of the related issues are plain out laziness in bug fixing, for example, it's still always a 50/50% shot if "permanent" buffs stick around after companion revival. It's been this way since release -- but a lot of issues also come and go.