Try 2.25-2.5hr wake windows at 6 months. Anything less and they crash before sleep pressure builds.

We did 'crib hour' - leave them in there even after the 30 min wake. Took a week but they learned to connect cycles.

30 min naps = end of one sleep cycle. Usually means wake window before nap is wrong - too short or too long.

Sometimes it's developmental - sitting up, crawling. Passes in 1-2 weeks usually.

Iron levels are worth checking if it persists - low iron disrupts sleep.