A motion is absolutely needed. It's not difficult to do but it's an important protocol change that will require everyone to upgrade.
I notice the difficulty has dropped a lot, any problem?
"difficulty" : 0.00015758,
I am 2422 block behind, am I on a fork blockchain?
You may indeed be on your own fork. I see difficulty at 0.00044973 with a current block height (at 21:12 UTC on the 10th) of 837526.
Are you still having the same problem or has it resolved itself?
I stopped mint, and ready to start v5.0.1.
I deleted my blokchain data and restart v5.0.3, hope it works.
I re-downloaded the blockchain and find my "balance" is there, but most "stake" lost, shall I wait for one week to receive my stakes?
Based on your previous report of very low difficulty, it appears your client was on a fork. I don't know why. However, if correct, you won't get any mint rewards from the time when you were minting on your own fork. When you join the main network, those become stales and will remain so.
Remain so? The sum of "balance" and "stake" is quite less than several days before. I"ll wait for some time.
EDIT: balance issue solved by backup *.dat.