18.12.1 Appimage Has Echo When Playing Video? Can I do anything for the appearance, fonts, icon size when using Appimage?

Do you mean an audio echo when playing the timeline? If yes, check if you have applied any effects by accident.

No it's a general stuttering related problem I think. Older version had better playback or perhaps this has something to do with automatic audio driver settings or something... Well meanwhile I keep using two versions. Perhaps I just have too old PC.

Yes we found some playback problems related to MLT. So keep the old version which doesn’t have this problem. BTW: which old version do you use?

I use 0.9.10 on Ubuntu 14.04.5 LTS. So everything is "old". Also 18.12.1...