mapping options disappeared

[Tassy]

Yesterday I could import files as "sequence" in 2C v8.1. 
Today import  menu mapping does not contain it. v6 does not contain it either.
Another problem that import random selects one file among the lot (mp3) telling " mixbus canot use one or more .."
I think this message "cannot use.. blabla.." does not allow sequenceing so it does not appear.
So the question is why the hell mixbus "cannot use..." some random files and when it is deleted from the list it chooses another one

And yesterday Mixbus had no problem with the same file
crazy

thanks
Tassy

[Tassy]

Another thing
Mixbus imports with no problem as "one track" the same file for which it told "cannot use...." if more are selected for a sequence.
any idea?
thanks
Tassy