Your website probably has an error caused by a plugin conflict. Hostinger is probably showing that error because there’s an error elsewhere already, which in turn is causing hostinger to show the error as well.
First and foremost it’s always best to update plugins/themes you’re using and see if you can save ur posts.
If it fails, You can try this to recognise the error:
Turn on debugging
delete wp-content/debug.log file (maybe through a filemanager plugin or directly from hosting or FTP).
Try saving the post
once your get the error, download your debug.log file, and look for “fetal error”. That’s your actual issue. Maybe share the result here.
