This happens occasionally and when it does, I usually find that the simplest solution is to add a standard cabinet against a wall away from anything else, add a simple rectangular benchtop to it and then move the benchtop to the main drawing and alter it.
I also notice from the images that your design is pretty huge. When designing in 2020 please try to remember that it is designed to show one or 2 rooms. Not the entire layout of a home all on the same floor plan. Issues like you are encountering are more likely to occur in designs that have compressed or overlapping placement zones or improperly connected walls. Just from the screenshot I can see several overlapping placement zones. If you limit the design to just the kitchen you will be much less likely to encounter issues like this.