Odd, it loaded now, but previously there were ~7 lines.
The logs show the download completing and showing up in history while extracting:
18-5-3 23:51:59.8|Trace|HttpClient|Res: [GET] http://localhost:8080/api?mode=history&start=0&limit=30&apikey=(removed)&output=json: 200.OK (20 ms)
18-5-3 23:51:59.8|Trace|HttpClient|Response content (1348 bytes): {"history": {"total_size": "3.1 T", "day_size": "18.9 G", "noofslots": 1, "last_history_update": 707, "week_size": "41.6 G", "version": "2.3.3", "slots": [{"action_line": "Unpacking: 48/48", "show_details": "True", "script_log": "", "fail_message": "", "loaded": true, "size": "739.4 MB", "category": "*", "pp": "D", "password": null, "completeness": 0, "script": "Default", "nzb_name": "Better.Off.Ted.S02E12.Swag.the.Dog.720p.WEB-DL.DD5.1.h.264.nzb", "download_time": 87, "storage": "", "has_rating": false, "status": "Extracting", "script_line": "", "completed": 1525405919, "nzo_id": "SABnzbd_nzo_wwewzp", "downloaded": 775287597, "retry": 0, "report": "", "path": "\\\\?\\D:\\Downloads\\incomplete\\Better.Off.Ted.S02E12.Swag.the.Dog.720p.WE", "postproc_time": 0, "name": "Better.Off.Ted.S02E12.Swag.the.Dog.720p.WEB-DL.DD5.1.h.264", "url": "Better.Off.Ted.S02E12.Swag.the.Dog.720p.WEB-DL.DD5.1.h.264.nzb", "bytes": 775287597, "url_info": "", "stage_log": [{"name": "Source", "actions": ["Better.Off.Ted.S02E12.Swag.the.Dog.720p.WEB-DL.DD5.1.h.264.nzb"]}, {"name": "Download", "actions": ["Downloaded in 1 min 27 seconds at an average of 8.4 MB/s<br/>Age: 196d"]}, {"name": "Servers", "actions": ["news.supernews.com=739.2 MB"]}, {"name": "Repair", "actions": ["[2668a4932b664436706dc77e9e03e15d] Quick Check OK"]}]}], "month_size": "38.6 G"}}
Then 90 seconds later it’s gone from history:
18-5-3 23:53:29.5|Trace|HttpClient|Res: [GET] http://localhost:8080/api?mode=queue&start=0&limit=0&apikey=(removed)&output=json: 200.OK (32 ms)
18-5-3 23:53:29.5|Trace|HttpClient|Response content (825 bytes): {"queue": {"noofslots_total": 0, "diskspace2_norm": "34.5 G", "paused": false, "finish": 0, "speedlimit_abs": "", "slots": [], "speed": "0 ", "size": "0 B", "rating_enable": false, "eta": "unknown", "refresh_rate": "1", "start": 0, "version": "2.3.3", "diskspacetotal2": "265.76", "limit": 0, "diskspacetotal1": "265.76", "status": "Idle", "have_warnings": "0", "cache_art": "0", "sizeleft": "0 B", "finishaction": null, "paused_all": false, "quota": "0 ", "have_quota": false, "mbleft": "0.00", "diskspace2": "34.48", "diskspace1": "34.48", "scripts": [], "categories": ["*"], "timeleft": "0:00:00", "pause_int": "0", "noofslots": 0, "mb": "0.00", "loadavg": "", "cache_max": "1073741824", "kbpersec": "0.00", "speedlimit": "100", "cache_size": "0 B", "left_quota": "0 ", "diskspace1_norm": "34.5 G", "queue_details": "0"}}
Looks like the history is being removed before Sonarr can import it. Sonarr relies on the history to know which downloads are complete and ready for import.