What you're experiencing is probably the new hairs growing in and pushing up the lighter/thinned out mane. Instead of doing one big pull session, it usually works better to pull a little here and there every few days all the time. The new hairs will grow back a little at a time all over the crest, so you won't deal with it pushing up the long hair in chunks. Plus your mane will look neat all the time ;)
For now, dampen the mane and put loose braids in it to get it on the correct side. In 2-3 days, take the braids out, dampen the mane to release the braid kinks, and rest a slightly damp towel over the combed mane while you groom. Gently pull the towel off by pulling down in the direction the mane is laying (mane on right, remove towel by pulling from crest towards floor on the right.) You're smoothing the hairs while you pull the towel down, so you don't want to pull out or up. If you do the damp towel trick regularly, the mane will get and stay trained.