Duplicate Web Part on SharePoint page

Recently, in my colleagues' projects,

When opening a page, we found that

The maximum number of Web parts for all zones on this page has been exceeded. With this information, when you use SPD to open the page, you will find that the same webpart has been repeated for more than 10 times,

 

How many Web parts can a page have?

The limit is customizable in Web. config file,
50 (default)-http://technet.microsoft.com/en-us/library/cc262787.aspx
100 (recommended max)-http://technet.microsoft.com/en-us/library/cc287743.aspx

 

Final reason reference

Http://vivek-soni.blogspot.com/2010/08/duplicate-web-parts-shown-in-sharepoint.html

 

Issue:
Using the same
Web Part zone guid multiple times whether in same page layout or a different
Page Layout wocould result into the Web part being shown up multiple times.

Resolution:

Ensure that
Every Web Part zone and Web part in your page layouts have a unique guid stored SS
Your site collection.