It is strange. My wallet is not fully synced but still staking mature coins.
Kinda strange. Can you post a screenshot please?
This is not strange at all.
What you are seeing is not 'current' staking, but what 'had been' staking, and the reward/transactions that had occurred as your wallet updates to the latest block in sync.
Any wallet cannot perform such actions as staking and mining with it reaching the rest of the networks blocks due to consensus.
#crysx