Cannot qualify lead after upgrade to CRM 2015 if a duplicate detection rule is active

Hi all,

lead qualify process doesn't work after upgrading to CRM 2015 (On-Premise). I tried several things out, which I found in this community or around the internet. When I click on the "Qualify" button and a duplicate detection rule is active for "Contact - Email", first nothing happens. When I move back using the back button in IE, I get following error message:

Microsoft Dynamics CRM Error Report Contents

<CrmScriptErrorReport>
  <ReportVersion>1.0</ReportVersion>
  <ScriptErrorDetails>
   <Message>Die Eigenschaft "get_errorCode" eines undefinierten oder Nullverweises kann nicht abgerufen werden.</Message>
   <Line>1</Line>
   <URL></URL>
   <PageURL>/main.aspx?etc=4&extraqs=%3f_gridType%3d4%26etc%3d4%26id%3d%257b16B955C7-856E-E611-8100-005056A74971%257d%26rskey%3d%257b00000000-0000-0000-00AA-000010001005%257d&pagemode=iframe&pagetype=entityrecord&rskey=%7b00000000-0000-0000-00AA-000010001005%7d</PageURL>
   <Function>anonymousr:DieEigenschaft"get_errorCode"einesundefiniertenoderNullverweiseskannnichtabgerufenwerden.</Function>
   <FunctionRaw>TypeError: Die Eigenschaft "get_errorCode" eines undefinierten oder Nullverweises kann nicht abgerufen werden.</FunctionRaw>
   <CallStack>
    <Function>anonymousr:DieEigenschaft"get_errorCode"einesundefiniertenoderNullverweiseskannnichtabgerufenwerden.</Function>
   </CallStack>
  </ScriptErrorDetails>
  <ClientInformation>
   <BrowserUserAgent>Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/7.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; InfoPath.3)</BrowserUserAgent>
   <BrowserLanguage>de-DE</BrowserLanguage>
   <SystemLanguage>de-DE</SystemLanguage>
   <UserLanguage>de-DE</UserLanguage>
   <ScreenResolution>1920x1080</ScreenResolution>
   <ClientName>Web</ClientName>
   <ClienState>Online</ClienState>
   <ClientTime>2016-08-30T09:46:50</ClientTime>
  </ClientInformation>
  <ServerInformation>
    <OrgLanguage>1033</OrgLanguage>
    <OrgCulture>2057</OrgCulture>
    <UserLanguage>1033</UserLanguage>
    <UserCulture>1031</UserCulture>
    <OrgID>{43EBC55A-B1FA-E311-AFAE-005056B21414}</OrgID>
    <UserID>{004ACAA1-EE1E-E511-93D6-005056A7238E}</UserID>
    <CRMVersion>7.0.1.170</CRMVersion>
  </ServerInformation>
</CrmScriptErrorReport>

When I click on the "Qualify" button without an active duplicate detection rule, it works fine!

Who can assist me on the issue to resolve it?

Best regards,

Karan5959