For a couple of years now I have been observing the rust accumulation on the engine mounts.  Looks nasty and it’s a pain to keep cleaning up.  But on closer inspection I could not see any structural failure and the rubber inserts appeared to be OK. So I just convinced myself that it was a cosmetic issue and everything was working well under the surface. Recently I had noticed that the engine was moving around on the mounts more than normal, the change may have been ongoing slowly so I hadn’t picked it up sooner.  Worn engine mounts cause more engine movement, the symptoms were there.