Issue resolved after knocking at Mikrotik support. They confirmed the destination path was correct but the source path was wrong. However, the router only returns the destination path is invalid. They informed me that /file/DHCP.rsc is wrong. It should be only /DHCP.rsc.
My final script was:
/tool fetch upload=yes mode=ftp ascii=no address=172.28.4.52 port=21 user=dontry password=Laptop#2022 src-path="/DHCP.rsc" dst-path="/backup/DHCP.rsc"