3ds Max :: Render Element Output Files - Format And Name

Sometime with some scenes, I have this trouble :

-when I render my beauty pass in TIF 16bits with render elements and when I leave MAX set my render-elements output files automatically, MAX use the initial name of the output beauty pass. So technically, It is suppose to make a couple of file with the same format and the same name.
-ok, I presse render to Backburner and I wait.
-Now my render is done, I go check my output files. And, sometimes, without constancy, my beauty pass is a TIF 16bits but my passes are in gray-scale or in 8bits or 16bits in random.

If I restart the job on Backburner, maybe it fix this problem, maybe not.

The unique thing I find to fix that is to set all my passes manually. but it's a pretty heavy process.