The 2.4.3 version of the plugin was only available for about 7 days (19 Mar 2016 - 24 Mar 2016) before it was superseded by the 2.4.4 version. I would be surprised if you were running 2.4.3, since it was replaced over two months ago by 2.4.4.
You should be able to see check enough of the plugin installation history from your "Manage Plugins" section called "Installed Plugins". If git plugin 2.4.3 was on your system prior to 2.4.4, it will be listed with a large button "Downgrade to 2.4.3" on the line for the git plugin.
If the version number in the "Downgrade to " button is not 2.4.3 (possibly 2.4.2 or 2.4.1 or 2.4.0), then you probably never had 2.4.3 on your Jenkins server.
If you never had 2.4.3 on your machine, then I don't have any good suggestions for the cause of the problem you're seeing.
Are there specific additional behaviors which are not preserved, or is it all additional behaviors that are not preserved?