[NSFW] SyntaxError: Invalid regular expression: invalid flags

Try disabling all plugins and enabling a stock wordpress theme (e.g. Twenty-Twenty). Clear the cache and see if the error disappears. If so, enable one by one until you identify the probem theme/plugin. You can use the Health Check plugin to carry out this troubleshooting in your session only, and without affecting the site for visitors.

Error is gone. Thank you!