The ‘Spark Lock’ challenges after you defeat Kaos in Woodborrow

Per an Activision rep on Reddit:

Swap Force uses an autosave feature that is explained when the game boots up. The autosave (console) occurs when there is a Progression - Chapter Completion, Challenge Completion or picking up a Collectable.

The toy saves every 30 seconds and when gaining XP, Treasure, Upgrades, Stat Boost and Hat pick up.

Based on their comment, there is no way to trigger it by entering/exiting an area of Woodburrow as there was in Giants, but another Redditor offers the following suggestion:

I turn subtitles on and off which triggers autosave. Still extra work but quickest I've found.

I have confirmed this to work.

I have the wii version also, and although there seems to be a few bugs with the wii version, this is not one that I know. I have completed the story mode fine with no real issues at all. The balloons you just walk up to and the skylander collects them. To put the fires out you need to flick the wii control to throw the balloons. If you are saying the balloons just fly away when collected as if thrown, I would suspect you are either moving the wii control too hastily or your control is perhaps faulty. Make sure the main wii control is fairly still whilst using the direction on the nunchuck to move round and collect the balloons. If you are sure you are doing this, then perhaps try a different control. I would always recommend a proper nintendo one, as other cheaper versions do tend to do odd things like this sometimes.