docs: add BUG-24 (OBD stall reconnect) + GPS replay jitter fix notes

BUGS.md

@@ -43,6 +43,21 @@ When CLOSED, move the entire entry to Resolved — don't duplicate.
   server holding 279 more raw points than the Pi — both documented in the original analysis,
   not regressions.
 
+### BUG-24 — OBD adapter stalls mid-drive; speed flatlines until the next ignition cycle
+- **Status**: `CLOSED` 2026-08-15
+- **Commit**: `b0ad6fd`
+- **Symptom**: on trip #8 (2026-08-13, 09:59–14:50), OBD speed went **102 → None** at
+  **14:14:31** and never recovered for the rest of the trip (~36 min). The log showed only
+  `No speed data received. #['14:16:35', 102.0]` — the ELM327 returned null speed responses
+  while still reporting `CAR_CONNECTED`, so the 10s reconnect loop never fired. Same stall
+  class as BUG-21 (which happened to recover on its own after ~20 min).
+- **Fix**: `obd_speed()` now counts consecutive null-speed polls; after 10 nulls (~20s) it
+  force-closes the connection via `_mark_connection_lost()`, so `_reconnect_loop` re-runs
+  `connect_obd()` and the adapter is re-handshaken instead of silently flatlining until the
+  car is restarted.
+- **Verification**: deployed to the Pi; the forced-reconnect path will be exercised on the
+  next real stall (in-car verification pending).
+
 ### BUG-22 — Trip max speed ignores GPS-only stretch (shows OBD max only)
 - **Status**: `CLOSED` 2026-08-14
 - **Commit**: `90cfd7b`
@@ -67,8 +82,8 @@ When CLOSED, move the entire entry to Resolved — don't duplicate.
   only the portal was missing it.
 - **Verification**: trip #9 points at 22:23:55 previously returned speed 0.0 — now return
   GPS-derived speeds (e.g. 61.9 km/h at 22:23:55, labelled `gps`). API rebuilt + healthy.
-- **Follow-up**: investigate why the OBD adapter dropped for ~20 min (reconnect on stalled
-  reads).
+- **Follow-up**: see BUG-24 — the adapter stalls and returns null speed without dropping
+  the "connected" status; fixed with a reconnect-on-stale-speed guard.
 
 ### BUG-20 — Server trip IDs inflate far beyond the real trip count
 - **Status**: `CLOSED` 2026-08-14