All of my current video files are either MKV or MP4 and either format shows the exact same behavior. I assume the behavior might be different with a DVD, but I don't have an easy way to test DVD playback at the moment.
I'm on a Win7-64 machine that has not had hardware changes and I've observed no correlation between this issue and other software. I cannot rule out conflicts, but this issue began immediately after upgrading to VLC 3.0.0. I do not run third-party antivirus/security software or anything else that seems likely to conflict. Also, I have tested the MPV player and it does NOT show this behavior at all.
Like many, I've used VLC for many years, but the upgrade to version 3.0.0 and newer somehow "broke" the jump backward/forward feature so that using the "Very short jump forward" feature "jumps" to the current start position perhaps 95% of the time and only rarely jumps forward. I get a repetitious "sampling" sort of effect rather than a forward jump. To achieve a very short jump forward, you need to very rapidly double-tap the hotkey (default Shift+Right). Doing two jumps very quickly will resume playback approximately one jump forward, but the timeline will still show the expected double jump for some number of milliseconds before falling back a few seconds to resume playback.
The issue occurs regardless of what the "Very short jump length" is set to, though a large enough jump will cause forward movement. What happens is that the timeline immediately jumps forward the desired amount of time, but then "falls back" a few seconds (more fallback with larger Very short jump lengths, but no more than 4 seconds), though it never seems to jump back further than when you started.
Example if Very short jump length (VSJL) is set to 3 seconds:
1:00 --> [Shift+Right] --> timeline shows 1:03 --> video glitches for a moment (? milliseconds) and then playback resumes at 1:00
If Very short jump length is set to 5 seconds:
1:00 --> [Shift+Right] --> timeline shows 1:05 --> video glitches for a moment and then playback resumes at 1:04
If Very short jump length is set to 10 seconds:
1:00 --> [Shift+Right] --> timeline shows 1:10 --> video glitches for a moment and then playback resumes at 1:07
It appears that since 3 seconds is very close to or less than the inherent "backward" travel before playback actually resumes, that jump length actually travels backward to your starting position rather than forward. I have NEVER observed the playback actually moving backward in time due to a forward jump, even if VSJL is set to only 1 second, so some logic must prevent this from occurring.
Note that this issue ALSO affects the time toolbar, so that clicking on the bar at a particular position might show 1:00 for just a moment, but then playback resumes at 0:58. It appears that the playback ALWAYS falls backward slightly whether a hotkey OR the time toolbar was used to make the jump.
This issue does not immediately occur while a video is paused and both hotkey jumps and the time toolbar appear to go to the exact position desired. However, resuming playback immediately "falls" backward slightly, just like when jumping forward or backward during playback.
The time ALSO falls backward slightly when jumping backward via hotkeys or the time toolbar, but this is less frustrating to the user since they intended to go backward anyway. Yes, I always get slightly more of a jump backward than I expected, but it's still more bearable.
I am confident that this behavior did (does) NOT occur with VLC 2.x or older. It could be coincidence, but it seems unlikely.
Thanks very much for your time.