NVMe Issue: Unable to change power state from D3cold to D0, device inaccessible

Yeah I havent actually touched APST but posted that bit of info as was mentioned in the thread, I just needed to disable ASPM. As you said NVME can run quite hot without power saving.
 
For anyone still troubled by this issue, upgrading the drive firmware to the latest version can resolve it. My drive has been running normally for two weeks after the upgrade (without any other special configurations). You can download the latest firmware from https://semiconductor.samsung.com/consumer-storage/support/tools/. Refer to https://www.reddit.com/r/DataHoarde...e_update_firmware_on_samsung_conusmer_ssd_in/ for installation instructions.
Tip: Make sure to run apt install unzip to install the unzip package so that Samsung's installation script works properly