I compared the sampled decompiles. Big caveat: the converted sample is from before the `move_entities` batching fix, so that specific issue is expected in these numbers.

**Blaring Differences**

1. **Converted snapshots are enormous**
   - Converted: `236,229` snapshot actions across sampled chunks.
   - Genuine: `4,949` snapshot actions across sampled chunks.
   - Converted `c1` snapshot alone has `220,755` actions, including `218,788` `game_packet`s.
   - Genuine snapshots are much tighter: `317`, `1467`, `1340`, `1825` actions per sampled chunk.

   This looks like the converter is carrying a huge accumulated packet history into later chunk snapshots, rather than a compact current-state snapshot like genuine Flashback.

2. **Converted snapshot contains `move_entities`; genuine snapshots do not**
   - Converted snapshot: `1` `flashback:action/move_entities`, payload `21,380` bytes.
   - Genuine snapshots sampled: `0` `move_entities`.

   Not automatically wrong, but it stands out. Genuine seems to rebuild snapshot state mostly through config/game packets and cached chunks.

3. **Timeline `move_entities` shape is wildly different**
   - Converted: `404,054` `move_entities`; payloads almost always `60-62` bytes.
   - Genuine: `22,753` `move_entities`; payloads commonly thousands of bytes, p50 around `3 KB`.

   This is the issue you spotted, and the previous patch should directly address it.

4. **Converted chunk snapshots are much larger**
   - Converted `c0.flashback` manifest:
     - `snapshot_bytes=4,110,813`
     - `timeline_actions=628,717`
   - Genuine `c0.flashback`:
     - `snapshot_bytes=229,550`
     - `timeline_actions=433,071`

   Converted has a snapshot about 18x larger than genuine c0 despite the genuine replay having lots of timeline activity.

5. **Genuine action table has an extra action**
   - Genuine includes `flashback:action/accurate_player_position_optional`.
   - Converted does not.

   I did not see actual sampled timeline rows using it, so this is probably not urgent unless first-person/camera smoothness is a goal.

6. **Metadata registry namespaces differ**
   - Genuine has `customNamespacesForRegistries` entries for `fabricskyboxes` and `xaeroworldmap`.
   - Converted has `{}`.

   This may be source-dependent, but it is a genuine-format difference worth remembering if registry/modded content ever looks wrong.

7. **Timeline packet profile is very different**
   - Genuine timeline is dominated by packet id `90`: `1,787,922` occurrences.
   - Converted has packet id `90` only `31,458` times, and instead has massive `move_entities` counts.

   Some of this is expected because the converter intentionally transforms movement packets, but the scale reinforces that movement handling was the big structural mismatch.

Most suspicious after the movement fix: **snapshot construction**. The converted chunk snapshots look much more like “all previous replay packets so far” than Flashback’s compact current-world snapshot.