gopro and dji files do not concatenate

[marava54]

Hello, i have this issue: when i try to append together two mp4 Gopro clips i obtain a file in which the first part (with the first clip) is ok, but the second part is made only of a static image for all the duration.
Evenly if i try to make the same with two mp4 taken with a Dji the first part is ok and the second is gray with some colored  noise on th top. I make in this way: I open the first file and then "file>append second file". I use ubuntu 16.04 and I have tried  Avidemux 2.6.20, 2.7.0 and the last nightly builds. Am i doing something wrong? Can someone help me to solve the issue?
thanks a lot

[eumagga0x2a]

If codec parameters don't match 100%, appending and saving in copy mode won't work and you will have to reencode.

[marava54]

Thank you for the answer. I try to append Gopro clip with another Gopro clip either taken with the same camera during the same action, the same with the Dji clips. Do you want the info that Mediainfo gives to me?

[eumagga0x2a]

MediaInfo output won't harm but also likely won't shed light on codec parameters mismatch.