I found that using files of my smartphone in Vegas leaves at ending the program a remaining memory problem in the background processes.

That remain must by hand be deleted before Vegas will open again.
I found that those mp4 files needed the so4compound plug in Vegas.

The files of my videocam are .mts and don't cause that problem at ending Vegas.
So I tried some things to get rid of that nasty problem by also changing the extension from .mp4 to .mts and now the same file with the new extension uses in Vegas the compound plug and no memory problems anymore.

Maybe something to try for users who have also memory problems.

NB. Of course is also very helpfull the Internal setting SO4 compound reader for avc/m2ts only switching to False.