We have released a new version v0.7.6-alpha fixing a few bugs that may make your node get stuck. So you definitely want to upgrade!
You probably don’t need to download the Chain snapshot manually, but if you really need, you can use https://storage.googleapis.com/nkn-testnet-snapshot/Chain_567511.zip
To update to the new version, please stop your nknd, rebuild (or download the latest binary from https://github.com/nknorg/nkn/releases), and then restart. If you are using the GUI miner or auto-updater, then you just need to stop and restart and miner and it will upgrade automatically.
For release details please see our Github: https://github.com/nknorg/nkn/releases
Feel free to ask any question here or preferably in our Discord: https://discord.gg/c7mTynX