Strangely enough, I had this problem on and off for a couple of weeks. It went to Subaru 🤦♀️. Came back as it could have been several things.
All of a sudden it started overheating, right off the scale, no heat coming out of heater, fan cutting out but on and off. Brought it home. Other half did a huge inspection after he filled up the water yet again. Had an airlock. So thought it was sorted, alas no. Did it again, same thing. In the end he found the smallest fracture in the top of the radiator. Could only just see it, right on the weld joint area ( not the right name I know 🙈) along the top, and not visible all the time. Had to leave it running for 30 mins checking all the time for water leakage but couldn’t see any. In the end he saw it just trickling down the side. End result.....new radiator put in...hey presto, all good.
Might not be the same but worth a good look. Would have had all sorts of things donee to it at Subaru!!!