Error after created user and edited user information

SharePoint FBA Pack
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1
I think there is something wrong with redirect because after I have edited information, it is saved to db. Same happens when creating new users.

Browser error: The resource cannot be found.
Description: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable. Please review the following URL and make sure that it is spelled correctly.

Requested URL: /_layouts/15/error.aspx

ULS error:
System.Threading.ThreadAbortException: Thread was being aborted.

System.Web.HttpException: The file '/_layouts/15/error.aspx' does not exist.
2
Check the sharepoint log file - there should be more details there as to what actually failed to cause the error. You might have some real issues with your SharePoint installation though - why would your error.aspx page not exist?