Hi @xxemuuu, thanks for flagging this and apologies for the delayed reply!
Are you still seeing this issue?
I just created a file using a a custom pattern fill, and it’s displaying within a Frame in the preview as expected. If so, what OS are you using? And are you using Figma in the browser or the desktop app? Are you able to share another screenshot that includes your Layers panel and more of the canvas?
With a bit more context, I can try to better reproduce the issue.