Hi @ll,
I conducted a few tests, mostly of them between 10 and 15 minutes and now I have a more clear idea about the issue, that whatever is what you experience, is all the same, just depends what software you use to read the file it will be more sensible to one of the problems or to other.
For me all this started when I tried to get the most quality possible in my recordings, so I increased the frame rating. Today I did the tests with the same game (WarThunder), always in a battle, just changing the frame rate of my recordings, and this are the results:
30 fps -> it never gets a problem. I remember I had this issue very rarely before, but not sure what settings I had. But in the tests conducted today, no one file had this issue.
50 fps -> some of the videos are free of failures, some have the extra unneeded GB at the end of the file, and my opinion is that is related to the real length of the video. Up to 5 or 6 minutes I havent errors. Over that I started to have the problem. GSpot reports exactly the 50 fps.
59,940 -> Similar to 50 fps, just when it fails the amount of unneeded Gb at the end of the file is magnified, duplicating in fact the real size that the file should have. GSpot reports 59,940 fps.
60 -> I havent samples of less than 5 minutes, all of them were between 8 and 16 minutes. All of them have the issue, the amount of unneeded GB duplicates the normal size of the file. GSpot, in all the samples reported a frame rate of 59,999, never 60.
To check that it was not a hardware failure I used 3 different Hard Drives, a very quick internal seagate, a external USB teradisk (but with more speed writing/reading than Bandicam needs) and finally an SSD drive.
Failure was exactly the same. It is related to the time of the record, not the drive where is recorded.
Also I had all units prepared for "performance", never go to sleep to save energy, etc...
The codec used was H264 and Motion JPEG. Same results, depending on how long the video, less than 5 minutes, could be fine, more will have problems.
Again: I could understand if my computer was slower enough to get a jerky video but I cant understand how that will translate in a duplicated size due to unneeded Gb of data (or just void data) at the end of the file.
Edited: Last minute test. All those tests were done with a quality factor of 80. Trying to do one in 30 fps and 100 Q it gave too the same error.
Also, dunno if this is related or not, but sometimes the fps overlay shows up exactly the double fps than really my game is running, recording or not. Checked it vs the internal game fps overlay and with razer fps overlay. And indeed, it is exactly the double figure.