Oh, and there are no jobs in the queue. Uploading a new version of the file does not appear to generate any jobs relevant to this, though, when using SMW 2.5.x (where the problem exists) or 3.0 (where the problem does not exist). The only jobs it generates are:
job_id: 266
job_cmd: recentChangesUpdate
job_namespace: -1
job_title: RecentChanges
job_timestamp: 20180914232556
job_params: a:2:{s:4:"type";s:11:"cacheUpdate";s:9:"requestId";s:27:"W5xDhLfkyYu4BqqyUK@9ZgAAAAY";}
job_random: 1398893290
job_attempts: 0
job_token:
job_token_timestamp: NULL
job_sha1: t0ui7t0cg0b9prp29q7plzaevrijg70
job_id: 267
job_cmd: htmlCacheUpdate
job_namespace: 6
job_title: Test_2.png
job_timestamp: 20180914232644
job_params: a:8:{s:5:"table";s:10:"imagelinks";s:9:"recursive";b:1;s:13:"rootJobIsSelf";b:1;s:16:"rootJobSignature";s:40:"038e9b9a072b7f6f5674aad13cdf91173c8ed6a9";s:16:"rootJobTimestamp";s:14:"20180914232644";s:11:"causeAction";s:11:"file-upload";s:10:"causeAgent";s:7:"unknown";s:9:"requestId";s:27:"W5xDtI2DZquTPPQ4ptCRIAAAAAc";}
job_random: 820376045
job_attempts: 0
job_token:
job_token_timestamp: NULL
job_sha1: qfv3vr0fn28whie2788uiy50x4a5mdy
On the failing server (SMW 2.5.x) I only saw the "recentChangesUpdate", not the "htmlCacheUpdate". On the working server (SMW 3.0) I saw both. In either case the jobs get cleared so quick I could have missed something, though.