Raw footage and proxy with different video length

Hi guys, I was wondering if you could help me trying to figure out how to solve this issue.

I am working in video production that started three years ago, so they did things old-fashioned way by converting the files through Media Encoder to ProRes 422 Proxy. Now we've changed the workflow to creating the proxy files directly from the raw footage through Premiere. The problem is that it is showing me 2 different video lengths. Raw footage has 12:37 mins and the proxy file 13:46. I don't know how this is even possible, but the result is that the file is inactive in some parts of the video.

I'm attaching the file properties info so you can understand what I mean.

The Premiere version I'm using is 2017.0.2

Many thanks for the help.