EtherCAT WKC-miss investigation instrumentation (IndraDrive).

Conclusion (2026-08-18): the misses are the drive not publishing a fresh feedback (AT) sample ~0.6% of cycles, in time-varying eras, on both bench IndraDrive units, present since the family's first contact with our master. The master was measured clean at every layer; the ctrlX showed zero misses under matched conditions. Follow-ups tracked separately: Bosch support case, and feedback extrapolation-on-skip for velocity-loop axes.

Instrumentation added (permanent field diagnostics, one stats block):

• Miss profile: category (noframe / untouched / partial), spacing, run length, last-miss timing context; counters reset per session.
• Arrival phase: frame arrival vs the drive's Sync0 from the drive's own DC timestamp, printed at lock and every report (verifies frame placement independently of the sync PI).
• Frame accounting: sent / received / cycle passes (proves one frame per cycle, no double-sends).
• Acyclic mailbox request counters (diagnostics / clear-error).
• ESC hardware error counters (0x0300 block) read per report, printed on change only: wire errors, processing-unit rejects, PDI errors, lost link.
• Config manifest: one line per bring-up with every value written to the drive (mode, telegram, scaling, modulo, cycle time) for comparing runs, builds, and machines.
• SoE procedure-command handshake logging (start/poll/cancel/end). Loop B trim re-enabled (experiment concluded); miss-experiment flag gbLoopBTrimEnable remains, default true.