Hi Scano,
Thank you for submitting this bug report and for providing that video. The first issue you mentioned is one the team is aware of and are currently investigating. I’ve a known issues post made here: [Known Issue][PS4/XB1] Loss of interactions
While there are no workarounds that we know of at the moment. Players have reported that over time the interactions come back as the issue seems to work on a cycle. You may also be able to interact with items if they are closer to the water level when the issue occurs.
Do you recall what time of day in game this issue triggered at and what you were doing at the time?
With regards to your issue with the giant crab, was this occuring during the interactions issue or beforehand? It may be possible the hitbox for the crab was also affected by this issue.
I understand how disheartening this issue is and while I know the suggestions above were not ideal, I hope they may be of some help while the team are working to resolve this issue.