Problem with fastforward/rewind in WebGui with .aac file.

I have used streamripper to capture live BBC radio streams and it produces the file type .aac. (In Windows the properties indicate that it is "MPEG-2 Advanced Audio Coding File). These play in Volumio but I cannot skip forward or backward with the control in the WebGui. I can drag the graphic around the circle but as soon as I release it, it returns to the current position of the playing track and the track continues unaffected. This control works correctly if I convert the .aac file to .mp3.
When I convert the file to .mp3 I use CBR and I’m wondering whether the .aac file is VBR and this is why the fastforward/rewind is not working.
The fastforward/rewind functionality is one of the main reasons that I was attracted to Volumio so I would really like to solve this issue, does anyone have any knowledge about this functionality ?

EDIT 14:50 I’ve found a work around.
Using ffmpeg to batch convert from .aac to .mp3 was taking far too long, so instead I now use ffmpeg to just copy the .aac file to the .m4a container, which is much quicker, this container plays in Volumio and I can now use the fastforward/rewind functionality with this file type as well.
I would still be interested in why the fastforward/rewind doesn’t work with my .acc files if anyone knows the answer.