On Lead form I've one BPF, inside that I've a contact lookup, while creating new contact from that lookup, quick create form opens and while saving from quick create I'm getting unexpected error shown below.

Also, Error details are as follows.
Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=8.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: System.Collections.Generic.KeyNotFoundException: Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #04D0F63FDetail:
<OrganizationServiceFault xmlns:i="www.w3.org/.../XMLSchema-instance" xmlns="schemas.microsoft.com/.../Contracts">
<ActivityId>286034a0-233b-4b4c-8404-44286eb0b47a</ActivityId>
<ErrorCode>-2147220970</ErrorCode>
<ErrorDetails xmlns:d2p1="schemas.datacontract.org/.../System.Collections.Generic" />
<Message>System.Collections.Generic.KeyNotFoundException: Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #04D0F63F</Message>
<Timestamp>2018-01-03T10:31:46.7732198Z</Timestamp>
<ExceptionRetriable>false</ExceptionRetriable>
<ExceptionSource i:nil="true" />
<InnerFault i:nil="true" />
<OriginalException i:nil="true" />
<TraceText i:nil="true" />
</OrganizationServiceFault>
Note:
1) All plugin steps on save of Contact has been disabled while testing.
2) All javascripts OnLoad and OnSave of Contact form has been disabled while testing.
3) All javascripts OnLoad and OnSave of Contact Quick Create form has been disabled while testing.
4) All Processes of Contact has been deactivated while testing.
Thanks in advance !
Bhayani