Sorry to say, but this won't help the devs at all, as you don't give enough details. I can't reprduce your error. You appear to have these two issues:
- The seed box does not appear when you start Light Mode
-> Which OS and version do you use? What error message do you see in the Console?
- After reinstalling IOTA, you aren't asked if you want to run full or light node.
-> Imo this is a minor issue, as you can always switch between full and light mode. If you are on Windows, make sure to delete everything in C:\Users\username\AppData\Roaming\IOTA Wallet and C:\Users\username\AppData\Local\Programs\iota after uninstalling. Then you will be asked again if you want to start in light mode or full mode after installing.