Conversion of 3g2 file fails, but thumbnail is created

I have setup the MIME type area of the universal settings using the following:

[avi, video/avi, 0]
[mpeg, video/quicktime, 0]
[mpg, video/quicktime, 0]
[mov, video/quicktime, 0]
[rm, application/vnd.rn-realmedia, 0]
[flv, flv-application/octet-stream, flash]
[playlist, 0, flash]
[wmv, video/x-ms-wmv, 0]
[3gp, video/3gpp, 0]
[3g2, video/3gpp2, 0]
[mp4, video/mp4, flash]
[dir, application/x-director, 0]
[dcr, application/x-director, 0]
[ogg, application/ogg, 0]
[youtube, 0, youtube]
[googlevideo, 0, googlevideo]
[brightcove, 0, brightcove]
[vimeo, 0, vimeo]

Do I need to add something here as well:?

flv-application/octet-stream
application/octet-stream
application/x-flash-video
video/x-flv
video/mp4
video/flv

For now, the flv is created with a size of 0 and I get the message that conversion has failed.

My global ffmpeg command is this:
-i @input -f flv -acodec mp3 -ar 22050 -ab 64k -ac 1 @output

and the global thumbnail command is this:
-y -i @input -vframes 1 -ss @thumbtime -an -vcodec mjpeg -f rawvideo -s "@thumbsize" @output

As that didn't seem to do the trick, I adjusted the content type specific command to be this:
-i @input -f flv -acodec libmp3lame -ar 22050 -ab 64k -ac 1 @output

but that didn't seem to help.

I'm using the dash player module, but I think it leaves all conversion duties up to this module and doesn't interfere.

Any ideas what's going on?