error during export : ERROR: Bad data width size. Report me!

hi everybody, i’v got a problem since few days and don’t know why.
when i export my session in one wave file , the log tell me :

“: ERROR: Bad data width size. Report me!”

got this in ardour 2.8.11 and mixbus 2.0.3 but not in ardour 3.0 alpha 9

any ideas ?

IDK

http://ardour.org/how_to_report_a_bug