No, Anvesh Ramaswamy, I cannot help you with any steps to proceed to resolve the issue. I requested 5 items and you provided far less than 1 of the items I requested.
I help Jenkins users on my personal time. When you fail to provide all the information I request, it tells me that you're really not committed to receiving my help.
Since you're running a Jenkins version that is many years old and a git plugin that is many years old, you should expect to do significant work of your own before I or anyone else will be willing to assist.
The information you provide in the issue report needs to be sufficiently detailed that it persuades me that you are investing enough of your time to justify that I should invest some of my time. You've not shown that. I will not engage in a long series of questions and answers about the issue unless you persuade me that the issue is very interesting to me.
If you decide that it is not worth enough of your time to provide that information, then let's agree that we'll close this issue as "cannot reproduce".
A job being started twice for the same commit might be an indication that the repository is using both notifyCommit and web hooks. It might be an indication that the repository is being polled in less time than the build requires to complete.
Please provide precise steps that will allow others to duplicate the problem you're reporting. Precise steps include: