Invalidgroup Exception Error while accessing interface

When i am trying to access when particular dashboardpage in interface for displaying active tasks i am getting the UI error saying like below and i could see group ids was not taking correctly and other thing is through Admin access the page was accesible but specific to group access it was throwing error

Expression evaluation error [evaluation ID = 36716:124d6] in rule 'ctest_test_pendingtaskgrid' (called by rules 'cmtest_fies_testdashboard' > 'cmyd_ets_dashboard_requests') at function 'getdistinctusers' [line 114]: [InvalidGroupException]

the code available at 114 line was this 

a!sideBySideItem(
showWhen:not(rule!APN_isBlank(ri!acceptedByGroup)),
item: a!dropdownField_20r2(
label:"Accepted By ",
labelPosition: "ADJACENT",
choiceLabels:apply(rule!Cfsdsd_getFullnameByUser_LastFirst,getdistinctusers(topeople(ri!acceptedByGroup))),
placeholderLabel:"--- Show All ---",
choiceValues:getdistinctusers(topeople(ri!acceptedByGroup)),
value: local!taskOwner,
saveinto:{ local!taskOwner,a!save(local!taskGridSelection.pagingInfo.startIndex,1)}

)),

the value passing to the ri!acceptedByGroup from parent was below highlighted:

rule!CMDS2_FBM_pendingTaskGrid(
label: "Cases Pending Pre Approval - Next Period",
processModelId:cons!CMDSFBM_PExxID_COEPPROVE,
taskName:cons!CMDSFBM_TN_CEO_PREAPPROVAL,
workstream:index(cons!CMDSFBM_WORKSTREAMS,1,""),
linkToTask_bool:true(),
batchsize:25,caseId:local!caseId,
acceptedByGroup:togroup({cons!CMDS_tetsts_Ctest_ATLAS_GROUP,cons!CMDS_FTestM_COE_COMET_GROUP}),
requestToBeProcessedFor:cons!CMDSFBM_REQUEST_TO_BE_PROCESSED_FOR[2],
selectedTasks:ri!selectedTasks,userAction:ri!userAction),