SharePoint 2013 discussion board list issue

we are using an OOTb discussion board list . and when we click on the unanswered tab it gives the error with corelation ID:

logs are

0x62F4  SharePoint Foundation           Authentication Authorization    agb9s   Medium      Non-OAuth request. IsAuthenticated=True, UserIdentityName=0#.w|adcouncil\umofarmacc, ClaimsCount=28 5c43589d-b0c1-30d1-cd87-5bd796a2c343
01/24/2016 09:08:55.45  w3wp.exe (0x1B48)                           0x62F4  SharePoint Foundation           Logging Correlation Data        xmnv    Medium      Site=/departments/it    5c43589d-b0c1-30d1-cd87-5bd796a2c343
01/24/2016 09:08:55.46  w3wp.exe (0x1B48)                           0x62F4  SharePoint Foundation           Performance                     ki9i    High        Query needs to have a WHERE clause with an NVP field if UseNvpForOrderBy is TRUE.   5c43589d-b0c1-30d1-cd87-5bd796a2c343
01/24/2016 09:08:55.46  w3wp.exe (0x1B48)                           0x62F4  SharePoint Foundation           Health                          46ri    High        Throttled:Big list slow query. List item query elapsed time: 0 milliseconds, Additional data (if available): Query HRESULT: 80070024 List internal name, flags, and URL: {7D30631C-AB31-4943-929D-B89AE6E20035}, flags=0x0020000820c01000, URL="http://srumos08/departments/it/_layouts/15/inplview.aspx?List={7D30631C-AB31-4943-929D-B89AE6E20035}&View={28C8175B-94A9-4EB8-A036-AF5C08D50092}&ViewCount=4&IsXslView=TRUE&IsCSR=TRUE&HasOverrideSelectCommand=TRUE&FolderCTID=0x012002001D0510CE0262EB46B96E5EA2E3FBBF3F" Current User: 1073741823 Query XML: "<Query><OrderBy UseIndexForOrderBy="TRUE" Override="TRUE"/><Where><Eq><FieldRef Name="IsAnswered"/><Value Type="Integer">0</Value></Eq></Where></Query>" SQL Query: "N/A"  5c43589d-b0c1-30d1-cd87-5bd796a2c343
01/24/2016 09:08:55.46  w3wp.exe (0x1B48)                           0x62F4  SharePoint Foundation           General                         xxpm    High        Unable to execute query: Error 0x80070585   5c43589d-b0c1-30d1-cd87-5bd796a2c343
01/24/2016 09:08:55.46  w3wp.exe (0x1B48)                           0x62F4  SharePoint Foundation           General                         8e2s    Medium      Unknown SPRequest error occurred. More information: 0x80070585  5c43589d-b0c1-30d1-cd87-5bd796a2c343
01/24/2016 09:08:55.46  w3wp.exe (0x1B48)                           0x62F4  SharePoint Foundation           General                         72k4    Medium      <nativehr>0x80070585</nativehr><nativestack></nativestack>  5c43589d-b0c1-30d1-cd87-5bd796a2c343
01/24/2016 09:08:55.46  w3wp.exe (0x1B48)                           0x62F4  SharePoint Foundation           General                         8kh7    High        <nativehr>0x80070585</nativehr><nativestack></nativestack>  5c43589d-b0c1-30d1-cd87-5bd796a2c343
01/24/2016 09:08:55.46  w3wp.exe (0x1B48)                           0x62F4  SharePoint Foundation           General                         aix9j   High        SPRequest.GetListItemDataWithCallback2: UserPrincipalName=i:0).w|s-1-5-21-2165195311-2691588097-3176437156-3628, AppPrincipalName= ,pSqlClient=<null> ,bstrUrl=http://srumos08/departments/it ,bstrListName={7D30631C-AB31-4943-929D-B89AE6E20035} ,bstrViewName=<null> ,bstrViewXml=<View><Query><OrderBy UseIndexForOrderBy="TRUE" Override="TRUE"/><Where><Eq><FieldRef Name="IsAnswered"/><Value Type="Integer">0</Value></Eq></Where></Query><ViewFields><FieldRef Name="ID"/><FieldRef Name="PermMask"/><FieldRef Name="Created"/><FieldRef Name="Modified"/><FieldRef Name="Title"/><Field ,fSafeArrayFlags=SAFEARRAYFLAG_AUTOHYPERLINK  5c43589d-b0c1-30d1-cd87-5bd7.

there are no any unexpected or critical exception coming . And there are no items in the unanswered questions tab. the list is not big , it just has 3-4 items in it . dont know whats happening

What permission level of the account you are using? Try to use another user with higher permission to compare the result.

And what authentication type you are using in this site? If ADFS has been configured, check the following link to see if this is the case: https://sharepoint.stackexchange.com/questions/79864/sharepoint-2013-adfs-login-local-token-cache-always-expired

Here are some more troubleshooting you can try: 
Check if the standard site features are enabled in this issued site. 
Then check if there are any customized solution in this site, sometimes they can cause conplicts. 
Also check the name of your discussion board is there are any special characters. 
Reset IIS and compare the result.

For more details, you can refer to the link below: https://social.technet.microsoft.com/Forums/en-US/74fd83cb-e8f8-4b20-acd9-ed0b16059e9b/discussion-board-error?forum=sharepointgeneralprevious