I reviewed the roles.xml, I see there are 6 tasks:
Create Group
Modify Group
Modify Group Members
Portal Modify Group Members
portalModify Group
View Group
With <Tab tag="Membership" tabdefinition="GroupMembership"> and all of them has
<Property name="GroupListScreen">DefaultGroupList</Property>
<Property name="GroupSearchScreen">DefaultGroupSearch</Property>
Except 1 task which is "Portal Modify Group Members" which do not have GroupListScreen and GroupSearchScreen under GroupMembership and GroupAdministrators tab
<ImsTask name="Portal Modify Group Members" tasktype="ADMIN" category="Groups" application="IMS" tag="PortalModifyGroupMembership" action="MODIFY" object="GROUP" searchscreen="DefaultGroupSearch" system="false" auditable="true" provisionable="true" workflow="true" external="false" hidden="false" public="false" checkscope="false" scopesecurity="GroupsAdminOf" autosynch="OFF" autoaccountsynch="OFF" webservice="false" priority="4" category2="Tasks" category3="" taskorder="0" categoryorder="30" category2order="0" category3order="0" automaticexecution="false">
<Tab tag="Membership" tabdefinition="GroupMembership">
<PropertyDict name="Config">
<Property name="Config">1</Property>
<Property name="Hide">0</Property>
<Property name="HideIfNotAdmin">0</Property>
<Property name="ListScreen">DefaultUserRoleList</Property>
<Property name="ManageMembers">1</Property>
<Property name="Name">Membership</Property>
<Property name="SearchScreen">DefaultUserSearch</Property>
<Property name="ShowAllMembers">0</Property>
<Property name="Tag">Membership</Property>
</PropertyDict>
</Tab>
Added the following lines in "Portal Modify Group Members" task, then reimported the task and the issue is resolved.
<Property name="GroupListScreen">DefaultGroupList</Property>
<Property name="GroupSearchScreen">DefaultGroupSearch</Property>
Note:
The XML should be updated only where the information is missing.