If you have configured Cargo to use sccache then you'll need to disable sccache support. Unset the RUSTC_WRAPPER variable in your environment before opening VS code. Run cargo clean from the Cargo workspace you are working from (nrf52-code/radio-app or nrf52-code/usb-app). Then open VS code.
If you are on Windows and get linking errors like LNK1201: error writing to program database, then something in your target folder has become corrupt. A cargo clean should fix it.