Pump Problems, Yuk!

About a month ago upon a site visit I made to an installation we did last October, I found the pump was not working correctly.  For no apparent reason, it was continuing to cycle on and off, when it should have just shut down awaiting for the irrigation valve or hose bib to open and call for water.  After discussing the problem with the technical folks at the supplier, I pulled the submersible pump out of the tank and returned it.  The supplier verified the problem and sent a replacement pump.  I installed the replacement pump and after a few minutes the submersible pump started doing the same thing.  I called the technical staff back and we lowered the water level to make sure the internal plumbing from the pump to the side of the tank was working correctly.  It was!  We also checked the floating extractor on the intake side of the pump and it was working correctly and there wasn't any air in the lines.  From the hose bib water flowed as expected.  But the pump still cycled on and off even though everything was off.  So this time I pulled it out again, the technical staff had me open it up to make sure nothing was stuck in the internal valve, and nothing was.  I closed it up and re-installed it one more time, taking my time to document the process and results.  The same issues happened again which wasn't surprising.  Next I decided I had enough with this submersible pump and after consultation with the client we decided to return the pump for credit as it was still under warranty.  We also decided to change the design and install an external pump.  After gathering all the parts, I installed the pump last week and am glad to say it has worked flawlessly since then.  When the hose bib or the irrigation valve calls for water the pump turns on as expected, and turns off, shortly after they stop.  I don't know if there is a moral to the story, but it was clear after trying to get the pump to work properly several different times without success it was time to develop and implement Plan B!  I'm glad we did and the new external pump came up and worked as expected the first time!