I also have this issue. Thought it might be due to mods, but I uninstalled all the mods I had and reinstalled the game and it still occurs. For some reason, this appears to affect the MC, but Astarion seems to be unaffected by the issue.
Here's a screenshot I took of a freshly created barbarian using dual wielding to attack Us, only the main attack appears in the log, but both the action and bonus action have been used. Also, the attack animation did attack with mainhand weapon then the offhand weapon.
https://drive.google.com/file/d/12kjtjwg0BkcZKxmUUxjQlnGF2DDcycYQ/view?usp=sharing
