You can't downgrade soldered RAM.

No. Soldered RAM is literally part of the motherboard. You can’t pop it out and swap in a smaller stick to test things.

The chips are surface-mounted and reflowed onto the board. To change them, you’d need a hot air station, flux, steady hands, and the exact same chip type from the same manufacturer. Even then, the board’s memory controller is often trained to the specific configuration — dropping from 16GB to 8GB might not even boot.

If you suspect a bad RAM chip and it’s soldered, your options are: run memory diagnostics (MemTest86), try software fixes (like disabling one channel in BIOS if possible), or replace the whole board. Downgrading to verify a bad chip is not a realistic troubleshooting step.

Save yourself the trouble. Run the tests. If the chip is bad, the board is the fix.