esprout, yoyo is right, the trend is for the long haul - but don't count it out yet!
You are right, it sounds like a bad contact, and it *could* be inside the head, but it could still be coming from something you can easily fix. Try this:
Take off the head and switch cap, and wipe off all of the lube from the tube. Then put a piece of fine sandpaper (320 to 600 grit silicon carbide wet/dry is ideal) on a flat surface. Press each end of the tube down on the paper and twist and translate to cut a fresh surface on the aluminum.
Now clean out inside the head and tail, especially on the flats up inside that the end of the tube you just sanded contact. Apply a light lube, vaseline is fine for 4-sevens lights, on the threads and O-ring. Put it together and give it a try.
If that is not making a difference, take the tail cap back off and get a piece of wire, paper clip is good, and bend it so you can hold it firmly between the back of the batteries and the end of the battery tube, keeping the light on. Now try your modes at the head. If that makes it work, the connection issue is in the switch. If so, with a pair of small needle nose pliers, you can grab the two holes in the aluminum ring holding the switch in and turn it. Sometimes, it is just loose. If it's tight, loosen and remove it, and dump the switch out. Then you can clean the mating surfaces between them. If that does not fix it, at least all you need is a new switch or whole tail cap from them, and your neutral head is still going.