Some of the more noticeable films might be an infection of some kind. Lactic acid bacterium gets mentioned frequently. Here's an excerpt from Jack Keller about it:
Oiliness or Ropiness: The wine develops an oily look with rope- like treads or strings appearing within it. It pours slowly and thickly with a consistency similar to egg whites, but neither its smell nor taste are effected. The culprit is a lactic acid bacterium and is only fatal to the wine if left untreated. Pour the wine into an open container with greater volume than required. Use an egg whip to beat the wine into a frothiness. Add two crushed Campden tablets per gallon of wine and stir these in with the egg whip. Cover with a sterile cloth and stir the wine every hour or so for about four hours. Return it to a sterile secondary and fit the airlock. After two days, run the wine through a wine filter and return it to another sterile secondary. Again, this problem, like most, can be prevented by pre- treating the must with Campden and sterilizing your equipment scrupulously.
I'd certainly be worried if it smelled funny. Lactic acid bacteria come from human saliva, among other sources. Lots of folks that mouth-siphon their stuff wind up with these type infections from time to time. Not saying that's what happened in your case, but it might be a possibility at some point that your mead got contaminated somehow.
I wouldn't take the visual description verbatim. Some infections can look completely different at different stages.
It could also be nothing, of course. Do you have any pics of it? Have you tried to get a sample of it and examine it more closely? Smell just that part? feel it between your fingers to see if it feels slimy or oily? If it's not just foamy then I'd start thinking contamination of some kind.
