Importing a WordPress 6.3 site with a block theme results in CSS not being loaded on the front end of the website with consequent display problems.
Export a Local Site that runs WordPress 6.3 with a block theme. Re-import the exported site file to a new sitename. In the site editor the display will look fine. On the front end of the website the display will show problems due to CSS not being loaded.
This appears to be a result of a new WordPress 6.3 feature that creates a transient called ‘_transient_wp_core_block_css_files’ in the wp_options table. This looks like it is used to cache a list of CSS files to load when using WordPress blocks. Local’s current process to rename the imported site do not appear to handle this, so the transient retains data for the original site. The solution is simply to delete the transient which forces WordPress to recreate it with correct data.
Problem the same on Linux and Windows 10. Solution works on both platforms.