This is one issue that bothers me a little bit, even though it’s probably very low on the list of priorities for site administrators.
With some collections, the ‘open next lesson’ function skips over some lessons. I’m not sure if it’s because they were added to the collection later, and then moved up on the list or what.
@ peterlaunonen - The lessons should be sequential. Is this happening in a specific collection only or is it widespread? If a provider has changed the order or uploaded lessons in the incorrect order and then not adjusted the order afterwards, this can happen. You could try contacting the provider and asking them to adjust the order.
Mark, I reported the same problem some days ago but no one seems to have noticed it. 
It’s widespread. I experienced it with “Anne of Green Gables” (the order of the lessons is correct) and Jolanda told me she had already experienced it with some Spanish lessons.
I can think of two off the top of my head:
The lessons are in the correct order when you look at the list, but when you are in a lesson and you open the next one, there are certain lessons that always get skipped.
Hi peter/mike,
Sorry about the delay in addressing this issue. The good news is that we now know why this is happening. It’s because the system is ordering the lessons based on when they were created, not based on their order in the Collection. We will get it fixed soon.
Thanks a lot, Alex!