Some of my proxy clips loses audio sync - why?

I am working with multiple cameras and proxies, having imported AVCHD sources from two cameras and mp4 from a third into separate folders.

It works so far fine, but for some reason a few of my clips lost sync on audio. When I check their original, no sync problems exist.

Proxies are made with GoPro and they, too, play back just fine and sync''ed when I locate the files on my harddrive.

But the clip in Premiere Pro CC 2018 has the sound descynced. Why? This is the 2nd project where I experience this, and I am not sure how to fix it.

Edit: I have cleaned out the media cache as explained in this post ​but it doesnt seem to help.

So, I delete the offending clip, and I try to ingest it again by locating it in the media browser. I make sure to open it in the source monitor to check it for sync problems. It plays back just fine.

So, Ingest! Now the clip works. But not with a proxy, I had to delete that.