Rendering that never ends - Adobe Premiere CS6

Hello Everyone,

I am editing a project in Adobe Premiere CS6 on a PC running Windows 7.

The videos that I am editing are all 4K in MP4 format.

When I have a PPCS6 project file saved to one of my EXTERNAL HARD DRIVES, I run into the following problem:  When I try to render a single clip, the render never ends. The rendering starts by saying "Rendering 1 of 1 Video Previews". When it gets to the end of the clip, it does not stop, but instead starts over again and says "Rendering 2 of 2 Video Previews". Then when that stops, it starts over again and says "Rendering 3 of 3 Video Previews". This is clearly a malfunction and very unusual. I have been using Premier CS6 for a long time and have not had this problem before. I have tried restarting the computer and the problem persists

However, when I have the same PPCS6 project file saved to the computer's INTERNAL HARD DRIVE, this problem does not exist, and the rending runs normally and finishes.

The external hard drive that I am using is BRAND NEW.  The same problem happened with another external hard drive, which is why I got the new external hard drive.  What could the problem be?  What is the solution?

Please note that I have been editing 4K MP4 footage for over 2 years now using the same hardware and setup, and this is the first time there has been a problem like this.  My computer has 12 GB of RAM and the Intel Core i7 CPU.

I would greatly appreciate any solutions that you might have.

Thank you very much.

M.S.