Your inventory weight may be inhibiting your ability to pick up/move a heavy object. It may seem counter intuitive but leaving the avatar/companion in your party with the highest weight capacity free of inventory will alleviate the majority of these issues. There are items in the game that are meant to be used outside of combat as well. Potions of storm/cloud giant strength (increase) potion of colossus (advantage) to strength checks in addition to character abilities/spells. Note that humans are granted a bonus to carrying capacity so the one with the highest Strength statistic may not necessarily have the highest Carrying Capacity. The game also has uses for some things and will not allow you to modify some object that would prohibit specific events. Many items that have a unique purpose have multiple ways to acquire them. When you have already obtained it or advanced the story/quest to where you should not have it, you see the 'item is unavailable" alert. This is different from when you cannot interact with an item due your size (either too small or too large). There are indeed still issues in the game, but do not be quick to call something a bug.
