Vertical video issue

I am trying to create tiktok videos with vertically shot videos on my phone and have encountered this issue again and again. After having success in beginning the process of editing, Rush will zoom out on my video creating black on both the left and right side, and in the process distorts my video size. I tried zooming back in to elimnate the black, but still distorted. I tried hitting both fill and fit, no luck as it considers the black on either side to be the normal size now. I am highly frusterated as I cannot find out what is triggering this to seemingly happen automatically, nor can I fix it. To best describe how the video itself looks, it looks pinched, everything looks very thin in the video. Length is not the issue here but width.

Can someone please help?