I am facing this issue and once crawler starts it shows this error after 2 minutes and then stops.
When i check logs I found error given bellow.
Exception: * System.ArgumentException: An item with the same key has already been added. at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource) at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add) at Microsoft.Office.Server.Search.Internal.Protocols.SharePoint2006.CSTS3Helper.ParseGroupCollection(XmlReader groupReader) at Microsoft.Office.Server.Search.Internal.Protocols.SharePoint2006.CSTS3Helper.InitSite(String strSiteUrl) at Microsoft.Office.Server.Search.Internal.Protocols.SharePoint2006.CSTS3Helper.GetSite(String strSiteUrl, sSite3& site) * 747c24ab-a84c-4c39-a6ac-7b75295dd41b
05/07/2021 12:16:45.10 mssdmn.exe (0x3D28) 0x2690 SharePoint Server Search Connectors:SharePoint dvt6 High SetSTSErrorInfo ErrorMessage = Error from SharePoint site: Unknown exception An item with the same key has already been added., CorrelationID: c67dc59f-74b0-b02f-cae2-acfff4ec664c hr = 80042616 [sts3util.cxx:7218] search\native\gather\protocols\sts3\sts3util.cxx 747c24ab-a84c-4c39-a6ac-7b75295dd41b
05/07/2021 12:16:45.10 mssdmn.exe (0x3D28) 0x2690 SharePoint Server Search Connectors:SharePoint dvu0 High STS3::StoreCachedError: Object initialization failed. Message: "Error from SharePoint site: Unknown exception An item with the same key has already been added., CorrelationID: c67dc59f-74b0-b02f-cae2-acfff4ec664c" HR: 80042616 [sts3util.cxx:7313] search\native\gather\protocols\sts3\sts3util.cxx 747c24ab-a84c-4c39-a6ac-7b75295dd41b
05/07/2021 12:16:45.10 mssdmn.exe (0x3D28) 0x2690 SharePoint Server Search Connectors:SharePoint ablzz High [STS3::COWSSite::GetSite] Return error to caller,URL=sts4s://betaportal.aku.edu/siteurl=/siteid={67ad6248-ba59-4f48-8f62-73197c91a616}, hr=80042616 [sts3util.cxx:2229] search\native\gather\protocols\sts3\sts3util.cxx 747c24ab-a84c-4c39-a6ac-7b75295dd41b
05/07/2021 12:16:45.10 mssdmn.exe (0x3D28) 0x2690 SharePoint Server Search Connectors:SharePoint dv62 High CSTS3Accessor::InitURLType: Return error to caller, hr=80042616 [sts3acc.cxx:1975] search\native\gather\protocols\sts3\sts3acc.cxx 747c24ab-a84c-4c39-a6ac-7b75295dd41b
05/07/2021 12:16:45.10 mssdmn.exe (0x3D28) 0x2690 SharePoint Server Search Connectors:SharePoint dv3t High CSTS3Accessor::InitURLType fails, Url sts4s://betaportal.aku.edu/siteurl=/siteid={67ad6248-ba59-4f48-8f62-73197c91a616}, hr=80042616 [sts3acc.cxx:289] search\native\gather\protocols\sts3\sts3acc.cxx 747c24ab-a84c-4c39-a6ac-7b75295dd41b
I did following steps but no luck
1) Removed https binding and check
2) removed web front end servers from NLB and then check
3) deleted search service application and re created
2) check rights of farm admin
Kindly help