‘Save Changes to Theme’ Wipes Custom Template

I am having a strange error where after I’m done working on a template design within the editor I go to use the ‘save changes to theme’ option so that I can apply them to the theme folder. But then it just completely wipes it and shows a blank template page with a ‘Pattern Placeholder’.

I’m at a loss as to why it does this, but I suspect it could be related to the starter theme I went with. I’ve tried across multiple instances of WordPress and still end up with the same issue. https://en-nz.wordpress.org/themes/blockstarter/ is the starter theme.

https://ibb.co/c3gLx2J
https://ibb.co/6PYs27J

• This topic was modified 1 year, 7 months ago by aiprofessional.
• This topic was modified 1 year, 7 months ago by aiprofessional. Reason: screenshots added