Corrupting audio after conversion

[smliuag]

When trying to merge the separate m4a files I have recorded into one m4b file while saving the chapter data it appears to be corrupting about the 2nd half of however many chapters are in a book that I am converting?
The first book I tried repeatedly with different settings it keeps speeding up the audio of the last 12 chapters so that it sounds like Alvin and the chipmunks. When I tried another book it then kept slowing down the audio of the last 7 chapters, so then not only does it sound awful but also even though it says it has the correct amount of chapters it actually cuts off the last few entirely cause the extremely slowed down audio takes longer and it cuts off where it would if it were playing normal speed.

I can't even anticipate if it's going to happen from the preview playback within the converter, it sounds normal until after the conversion is complete and I can't understand why.

[yermak]

I can only guess what could go wrong here...
I would say - you may be combining m4a files of different quality, bitrate, sampling frequency...
My suggestion would be to try to use:
Options Tabs-> Force re-encoding->Always.

Alternatively program tries to optimise m4a to m4b encoding buy just concatinating files. Selecting Always will force to re-encode all files to same quality and not just concat them into single container...
Frankly speaking - I have never tested such behaviour...