My Moondrop Kato cables also had this happen to them. In my case the outer sleeving popped out, pushed against the connector and strained the wires, and then the inner cable sleeving wore out and now the cable looks somewhat like this.
I suggest replacing with a cheaper Tripowin cable, the Grace cable has been pretty good to me so far, but I think a plug with a longer insert might be better.
I've been thinking about making custom iem cables now that I'm comfortable with headphone cables... but sourcing every part in low quantity is pricey.