I have been having reason issues with Avidemux 2.7 every edit I try crashes the program. I go though the editing changes the resolution and the size of the video and convert save the file never starts to convert than crash the app. What file is needed to see what is going on never has this happened before?
No-one can advise you based on the information provided.
Which version of Avidemux, Operating System, Work Flow, Media Info, Log Files etc?
If on windows, look for a file called admlog.txt in your account folder.
Something like AppData\Roaming\avidemux or AppData\LocalLow\avidemux.
That file might help.