Audio out of sync after making new mkv

[shadowonfire]

Hello!
I'm a total newbie to all this and I need help.

I've got some mkv files with two audio streams - english and russian and I want to remove the russian one. I've searched this forum and downloaded mkvtoolnix. I used mkvextractgui to extract the video and english audio track and then put it back together with mkvmerge. It went well, so I watched it. The first half was okay, then the audio started to get slightly out of sync, then even more and it went totally off in the end. I've watched the original mkv (with two streams) to make sure it's okay and it was perfectly synchronized from beginning to end.
What have I done wrong and how can I fix it?

[rnb5500]

Instead of extracting the streams with mkvextract, try loading the mkv directly into mkvmerge deselect the audio stream you don't want then remux it.
See if that works better.

[shadowonfire]

Well, that was pretty easy. It works, thank you very much!