SH404 in Joomla gets very strong cache, which would sometimes becomes very annoying for some changes you have done in the component. Even purge may not resolve the problem. So, the only way is to remove the data from database? No, try this first... Go to /components/com_sh404sef/cache using your ftp and you will see a php file with a random name like shCacheContent.3646bcbaeafd4912a132bbdcfbda9bab.php. Delete it and the cache of SH404 will be gone.