Hi, I’ve experienced the same problem and I was able to solve it myself, I like messing with stuff. So yeah, I’ll go in details like what could be causing it and how I solved it and what not…
My Warcraftlogs.txt file was 1.39GB in size, I had no internet or computer issues, it worked perfectly. Then I wanted to upload my latest boss kill, so I started scanning the log (this is when you name your log and click GO!), this is before upload of the actual kill, like when u choose which boss kill(s) u wanna upload, it was before this. Regardless, the issue should be the same, whether you’re scanning ur logs file or uploading. Basically, it got stuck at 86%, I’ve read/heard that many people have had this issue, but there was no fix for this on the forums, I don’t even know if those people fixed it, so I’ll write the fix.
What I assume is happening to the file while your Warcraftlogs Uploader is scanning it, is that, it is too big and it is having problems to scan it, it usually takes seconds, when it’s bigger than 1GB then it starts working slowly, bigger the file is the longer it takes and higher the chances are that this will happen. Yes, I took the time out of my life to test this. Some people get this bug earlier, like at 1.1GB or so, some get at 3GB or more, doesn’t matter. From what I’m seeing, it is the issue with the size of the warcraftlogs.txt file.
Solution: Yes, you’re 100% safe, nothing is lost. Open your Warcraft Logs Uploader -> click Split a Log, wait for it to do its job, when it asks you to achieve or delete the current file (click achieve), it will save it in your logs folder. Apart from that, it will split another copy of the same file into pieces, like one piece for each boss kill or something, there will be a lot of small files, that’s alright, it’s easier like that anyway. You’re done! If something like this happens just keep doing the same thing. To find the kill u wanna upload, just select the file u want, it is sorted by date, starting from oldest to newest.
Those small files are just same combat logs, they’re just split into small pieces, make sure to select which one you wanna upload when u normally upload your logs. Those files are in the same folder as your combat logs that u normally upload. It’s in WoW folder -> logs. That is where those small files are gonna be that u wanna select (if u did split your combat log that was bugged/stuck at %). Your achieved file that you fixed will be at WoW folder -> logs -> warcraftlogsarchive. That will still be bugged, not changed at all, but you can keep it 'cause updates might fix the program so that it gets better at handling bigger files. That file that you’re keeping is NOT corrupted, it is just too big to handle (that’s what I think and that’s what it seems like), but I’m not 100% sure about that, just keep it, that file is healthy.
Hope this helps