TikTok Studio Low Quality

I’m trying to migrate old instagram posts to TikTok, I found the best way was to just schedule one post from my instagram to upload onto TikTok a day through TikTok Studio. My issue is that all the posts that are scheduled to release get absolutely butchered in quality. I mean frames stutter freeze or skip and everything gets significantly more grainy than what I uploaded. Do I need to manually upload or is there a decent workaround for this? I’m pretty bummed that this is harming my content.