I blend the same kind of berries into smoothies all the time with zero problems. Citrus pips (like orange or lemon seeds) shouldn’t be any problem either. I don’t think I’d go throwing avocado pits in there but some tiny little seeds can’t possibly cause any trouble.
If it’s jamming with the mix you mention I would suspect the ice cubes. Try adding them gradually and make sure you’ve got liquid in there first (otherwise the ice cubes can go right to the bottom and possibly jam the blades).
Next time I make a smoothie, I’ll blend the ice, protein powder, and soy milk first. Then I’ll add the berries and blend some more. See if that fixes the issue.