I was trying to search this but could not find anything… I lost my checkpoint from all my playlist including LASO!!! I have 8/11 done for LASO but its forcing me to start from the beginning even though it says 8/11 completed.
Does anyone know how to fix this issue or is this a lost case? Please help!! 
Same problem here on Halo CE Legendary campaign playlist. I play together with a friend on my console and at the end of the last mission an update of Halo TMCC crashes my stats. So it show 9/10 completed. Now i can play the complete playlist again.
The problem is, that you cant select specific mission out of a playlist. Thats so annoying.