The first versions of Nebra indoor miner came with CM3 (Raspberry Pi Compute Module) embedding eMMC memory. As you may know, Helium has been really I/O intensive, particularly this summer when the blockchain was filling really fast the small amount of storage the CM3 has. As a consequence, all my Nebra indoor miner dead around the same week. Diagnostic seemed to be a storage failure.

Here is the story about making them live again