A little more information could be helpful and we have many systems working that are not behaving like this. So what version of DSS, what is the Authentication method, what groups are we talking about Global, Local GID's....., Was this working before and groups retained themselves in past then now groups are not saving? Are you receiving any errors (bottom of left side of the screen).
I have systems working with holding groups in versions 1.10, 1.15, 1.18 and 1.21