Orion Water Chiller

I am currently trying to purge and clean chiller after long time no operation use. There were water with impurities and sediments in the tank. I cleaned them and replaced with new water. Decided to do the discharge pump ONLY OPERATION for 10 mins to purge it and drain the water after that.

I am facing a problem regarding the water chiller. When I activate the discharge pump, the chiller activates for a short period of time and then it error comes out E03. From the manual, I learnt that that error is for discharge pump thermal relay.

Could there be problem with long piping for inlets and outlets? Long pipe might cause head loss. Not sure whether it is the main problem.

If the pump is stuck/ seized, do I have replace it? any better solution

I have contacted the manufacturers and received a troubleshooting method. However, I would like to be sure of the actual problem that might cause this. Has anyone has any background in this? Please do clear my doubts