When you open SE File from any folder then every time the file opens in a new window.
for eg: Open a part(PART1.PAR) file from the folder it will be opened in Solid Edge. When he wants to open it's draft file(DRAFT1.DFT) it opens in a new window of solid Edge.
Due to which the link between solid edge draft file and part file is not working.
Solution On the system where Solid Edge is opening in multiple instances; please take a backup of following registry and replace those registries with the registries from that machine on which software working properly.
Replace registries for .dft, .par and .asm from below location from registry editor from following location.
Notes and References 9149340
Hardware/Software Configuration Platform: INTEL
OS Version: 764