why SEO URL changed after clear cache ?
I believe that clearing cache should not affect to the SEO URL, because they stored in the database. You should contact your developer to solve this problem.
its changed after product update ! any answer ?
Which version of the cart are you on? Are you using V3 by any chance? There was a bug fix issued which resolved this issue in 3.0.4 or 3.0.5…and it has nothing to do with clearing the cache.
ver 3.0.4 use