Hi @hodain ,
That sounds really weird and I don’t know what’s happening.
Did you try Mirroring U and V in the Modifier?

What was the order of the Modifiers, before you Applied the Mirror?
You may need to post a link to your .blend file (via Dropbox, Googledrive, or so). Make sure to (File > External Data >) Pack Resources, Save the file and then upload.