After playing the classic mode once, this is my list of bugs and problem found:

1) Voice line problems

When you ask Red Prince what should be do now, there is only text.
He said search for Brahmos but there is no voice.

b) X:631, Y:51, the rat don't have voice line.

c) X:610, Y:729, the academy library, Lohse is missing voice line
'Jump to conclusion ....', when the player and companion are having a discussion.

d) In Arx, Elven Pilgrim looks like a female elf, but he/she had a male voice...

e) X:456, Y:623, Arx sewage, the narrator is missing voice line.

f) Arx, Brother Lyle is missing one voice line: 'It's the Lord Arhu's creation. ....'

2) Problem with journal and log:
When you move from Reaper Coast to Nameless isle.
The journal log is not updated on screen (GUI issue) when you clicked those closed log.
So the logs from different quests are shown (mixed) on the same screen.

3) The subtitle for the scene is missing when the ship travelled to Arx.

4) In Arx

a) No trader sell Polymorph spell books, omg!
The trader Aravae in Arx or Almira in Hall of Echoes sold the same types of spell books but no Polymorph. In my case, trader Friel was gone.

b) the old lady house
You can go from the inside of the house to the entrance of the basement.
The last door had indicated red color, but you can just walk through it.
Coordinates, about x:445, y:295.

5) Arhu
After rescue him. I visit him in his home.
On the first time, he looks fine.
After a while, when I visit him again, he is putting his hands on his head, looks like having a headache.

6) Saheila
In my walkthorugh, Lohse gone out of control and take out Saheila in Fort Joy.
But I see Saheila again in Arx..
Like Alexandar? Can died and revive?

7) Final battle
The game hangs when the Red Prince's dragonling use flight on top of those rocks.
Music is still on and pressing escape key recovered (after a while).
Tried multiple times.