If the groundwork hasn’t been done properly, your dog might start showing resource-based problems. This is where a dog's natural instinct to guard the things it values – eg, food bowls, toys, territory, and people – leads to behaviour problems.
You might need to remind your dog that hands come to give – rebuild this association by letting them see you put their food into an empty bowl. They should then eat the food piece by piece from that bowl so that they can understand that you are giving, not taking, their food.
Does your dog feel safe? Is there anything that is making them feel threatened? Consider where their bed is. You may have placed it somewhere aesthetically pleasing, like by the back door, but is this actually a quiet area where your dog can rest and feel secure?