When there are enough players in the Dynamic Groups list, there is a small auto scroll issue.
The list box will snap to the element which is highlighted, effectively rendering the vertical scroll bar useless. Current workaround is the up-down arrow keys.
Join a server using BIS Dynamic Groups which has enough people to exceed what can be seen in one frame of the list box.
Here are 3 servers afflicted currently (vanilla)
119.252.190.118:2882
31.186.251.92:2302
95.172.92.110:2302
This is such an annoying issue, especially on I&A servers that make a lot of use of the group management