dolphin pattern

by randy
(alto mi)

I just bought a pre-owned dolphin. My old died after 10 years and i liked it so much I bought another one. But this one only wants to go to the deep end and go side to side and thats it. Doesnt go up the sides either. Any ideas what might be going on? Clean filter bag, no kinks in the cord. I moved the handle position back and forth but no change. Anyone have a ideas?
Thanks
ADMIN REPLY: ASSUMING an exact replacement, a lack of suction will prevent the machine from climbing out. Could be debris jammed in and around the impeller vent at the top of the robot. Run the robot without the bag and see if it makes a difference too.