Does the tablet stay all mushy at the bottom once its finshed?
Also does it seem to get hot and dry at the end of the cycle?
Ok that's fine it does help a little as I know its not a heating fault.
Next time you use the dishwasher turn the spray arms in there so they face front to back and set it going.
Once its washing carefully open the door and see if the arms have moved position. Try it a few times and see what you find and let me know.