"Missing files" (file sizes mismatch) error when qBittorrent restart and torrent progresses back to 0%

[ccloli]

qBittorrent version and Operating System

• qBittorrent v4.1.4 (also in v4.1.5)
• Windows 10 (1803, x64, lang: zh-CN)

If on linux, libtorrent and Qt version

N/A

What is the problem

When qBittorrent start up, a bunch of torrents show Missing files, and execution log lists as File sizes mismatch for torrent '${torrentName}', pausing it. or Fast resume data was rejected for torrent '${torrentName}'. Reason: ${torrentName} fast resume rejected. check resume(): missing or invalid 'file sizes' entry. Checking again...

After the file is checking completed, the status is still Missing files.

Once qBittorrent restarted, its progress still shows 0% with Missing files status (on screenshot it's rechecking again).

What is the expected behavior

The torrent should not be "Missing files", or should be marked as "Completed" after verification and won't restore after restarting.

Steps to reproduce

At this time I cannot reproduce it. I've tried making a new hard link on a same volume (mklink /d /h /j D:\source D:\target) or different volumes (mklink /d /h /j D:\source C:\target, which is my case) cannot reproduce it.

If I've got something new, I'll note them here.

Extra info(if any)

• All the affected torrents are from a private torrent server (PT), but not all of them are affected, and the failed ones are not all in a same folder (W:\BDRip, W:\Music, W:\Book, etc.).

• The files were downloaded to W: drive when I'm not using hard link. Then I bought a new HDD labeling H:, and move them from W: to H: without opening qBittorrent, and run mklink /d /h /j W:\BDRip H:\BDRip to create a hard junction link.

• Both two HDD are installed on an external hard drive case, and connected to the laptop with a USB3.0 cable. It happens because I forgot turning on the HDD case, or say I started qBittorrent without connecting those drives. When I found it I closed qBittorrent immediately, and turn on the HDD case. When I launched qBittorrent again, all of my torrents are rechecking, and when I restarted qBittorrent once again, some torrents that has been rechecked still shows 0%.

• I made some torrents that < 2GB fixed by rechecking a few times, they're not in Missing files status any more. However I'm not sure how to make it works again, and only < 2GB torrents are fixed is just because they're small, so I paused larger torrents and recheck the smaller ones first, then they're just fixed in magic. I'm not sure it's related to torrent size.

• It happens in v4.1.5, once I found the bug, I downgraded it to v4.1.4 but still no luck.

• It happens a few months ago (should before Oct 2018).

• As qBittorrent says File sizes mismatch, is it possible to print the expected file size and actual file size so that I can find some relationship?

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