Occasional drops driving me nuts

[DumbAssMule]

Diagnostic help very much appreciated. When I screen some films I loose sound for up to one second sometimes. The picture remains in motion. This happens on multiple films and typically a couple of times in a 2 hour movie. Occasionally the disturbances are no more than a millisecond’s crackle.

The films are screened from .MP4 on a Windows 11 Pro laptop. I have tried some non-fixes already: removed all background processes that I feel I can, reinstalled Windows, switched laptops, swapped HDMI cables, used different player software, used different editing software - each time the issue reappears.

The process is that I rip a brand new Blu-ray using MakeMKV; the resulting file has no audible sound so I convert to .MP4 using Handbrake. I then edit using PowerDirector 2025 to add subtitles where necessary for the people I support. For long films I insert an interval. Our player of choice is VLC although I have tried Windows Media Player. All these are the latest versions of licensed software.

I have brought the laptop home (thereby excluding the equipment at the hall where I screen the films) and see that, in the last film at least, the 1 second gap always occurs at exactly the same place. However 11 ish times out of 12 there is no problem at all !

Given that let location of the disturbance appears to be random in a 2 hour film and even then only occasionally apparent, identifying and reproducing the issue is seriously time-consuming. Currently at wits' end.

Could PowerDirector 2025 Ultimate be messing with the exported file in such a way that some unknown other parameter (e.g. timing issue, concurrent background process) causes this ?

[DumbAssMule]

Update: I have tied the problem down to a file that is created by powerDirector and played by VLC. Swapping either of those programs causes the problem to disappear. Alas, I need to create at least 5.1 if not 7.1 audio, so I need PowerDirector.

An example of the problem may be found at
https://drive.google.com/open?id=1f1vJzPYjJ61VrDzstRdg1zrurPLsf7rU&usp=drive_fs
On that video the same sequence is played 12 times without problem, but on the 13th time I rewind (1 min 55 secs in) there is the silence; this is a typical frequency for this to occur. I have experienced this on 3 separate Windows 11 computers.

[davexnet]

Did you loop that 10 second video using VLC controls? Seems likely it's a VLC problem
since the problem doesn't occur when playing in another video player

[DumbAssMule]

It's a combo of VLS and PowerDirector as removing either resolves the issue. I didn't loop, I just hit the left arrow to rewind by 10 secs in VLC to keep passing over the same place. I'm guessing Codec, compression or frame rate incompatability but I know nothing.

[davexnet]

Perhaps you should post a sample cut from your actual source that shows the problem.