Wipe disk on NAS 326

I tried to upgrade my NAS 325 from 2off 2TB (RAID 1) to 2off 4TB but it did not work, so I have ended up with two 4TB disks that have valid linux_raid_numbers. I have now purchased a NAS 326 and want to try again. However, since the 4TB disks have valid linux_raid_numbers I want to wipe them before trying to transfer the data from the 2TB disks. If I install a 4TB disk in the NAS 326 and SSH to it, fdisk tells me "/dev/sda2: device contains a valid 'linux_raid_member' signature, it's strongly recommended to wipe the device by command wipefs(8) if this setup is unexpected to avoid possible collisions.". Unfortunately BusyBox does not have the wipefs command. So, how can I wipe the disks?

#NAS_May_2019