I have 2017 Bolt with 16K miles on it, and I recently experienced a sudden range drop of about 40 miles, which given my ~4.0 Miles/kWh average suggests the battery has lost roughly 10 kwH of capacity, or 16%. I was sufficiently concerned to buy an OBDM adapter and TorquePro, which confirmed that I have a bad battery cell. The car went to the dealer on Friday, but they haven't yet gotten back to me with their own findings.
The interesting question is whether this is a standalone failure, or related to the fact that my Bolt's on-board charger unit (which converts AC power from the ESVE to DC before it's routed to the traction battery) failed in rather dramatic fashion this past July, creating a dead short during charging. My Clipper Creek ESVE was smart enough to detect the problem and shut down, but when I attempted to troubleshoot that shutdown using the 110V ESVE that came with the car, I saw smoke and an orange glow coming from the motor compartment before hurriedly unplugging the unit. GM did repair the car under warranty, although it took almost a month as GM's product claims division, which AFAICT gets involved with incidents that have potential legal repercussions, felt the need to investigate. After the repair, all seem fine unit mid-October, when the range drop noted above occurred.