Olivier, I'd be pretty sure that's because of using the 'direct to' feature. 

If you split the route into 2, one part before what I presume is a train? and one part after you'll be able to see the elevation profile for both 'halves'. If both 'halves' are in the same folder you can see the 'whole' journey - especially if you recreate the stretch between viapoints 1&2. 

Hi Hobbes, thank you for the trick - it works perfectly. Actually that bug is not a big deal for me, I just wanted to mention it so that Richard can keep busy when he's bored ;-)

Ah… I think I’ve figured out why that is. It basically seems to happen when you use the ‘direct to’ feature, and the via points on either side have an elevation difference of more than 300m. I will see if I can fix it – thanks for spotting.

I’ve worked out a fix for this but it’ll need the server to go down for five minutes or so, so it’ll go live in the next day or two. Thanks again!

Excellent, thank you !