APPOINTMENT RECORD ISSUE - On Save Record Is Unavailable

Here are the steps I took when I encounter the issue.

1. Create Appointment
2. Save Appointment 
3. (Without doing any other action to the appointment record) Click Next Stage.
4. Record Is Unavailable Error occurs (logs below)

Note: When I refresh the form, it opens a 'New Sales Call' instead of just refreshing the current record.

Unhandled exception:
Exception type: System.ServiceModel.FaultException`1[Microsoft.Xrm.Sdk.OrganizationServiceFault]
Message: new_bpf_962fa5b399b048f59c8a425ed1c562d7 With Id = 00000000-0000-0000-0000-000000000000 Does Not ExistDetail:
<OrganizationServiceFault xmlns:i="www.w3.org/.../XMLSchema-instance" xmlns="schemas.microsoft.com/.../Contracts">
<ActivityId>14d81039-bf63-464d-922f-674d5625b5dd</ActivityId>
<ErrorCode>-2147220969</ErrorCode>
<ErrorDetails xmlns:d2p1="schemas.datacontract.org/.../System.Collections.Generic">
<KeyValuePairOfstringanyType>
<d2p1:key>ApiExceptionSourceKey</d2p1:key>
<d2p1:value xmlns:d4p1="www.w3.org/.../XMLSchema" i:type="d4p1:string">Plugin/Microsoft.Crm.ObjectModel.BpfBusinessEntityService</d2p1:value>
</KeyValuePairOfstringanyType>
<KeyValuePairOfstringanyType>
<d2p1:key>ApiOriginalExceptionKey</d2p1:key>
<d2p1:value xmlns:d4p1="www.w3.org/.../XMLSchema" i:type="d4p1:string">Microsoft.Crm.BusinessEntities.CrmObjectNotFoundException: new_bpf_962fa5b399b048f59c8a425ed1c562d7 With Id = 00000000-0000-0000-0000-000000000000 Does Not Exist ---&gt; Microsoft.Crm.BusinessEntities.CrmObjectNotFoundException: new_bpf_962fa5b399b048f59c8a425ed1c562d7 With Id = 00000000-0000-0000-0000-000000000000 Does Not Exist
at Microsoft.Crm.BusinessEntities.BusinessProcessObject.Retrieve(BusinessEntityMoniker moniker, EntityExpression entityExpression, ExecutionContext context)
--- End of inner exception stack trace ---
at Microsoft.Crm.Extensibility.VersionedPluginProxyStepBase.Execute(PipelineExecutionContext context)
at Microsoft.Crm.Extensibility.PipelineInstrumentationHelper.Execute(Boolean instrumentationEnabled, String stopwatchName, ExecuteWithInstrumentation action, PipelineExecutionContext context)
at Microsoft.Crm.Extensibility.Pipeline.&lt;&gt;c__DisplayClass2_1.&lt;Execute&gt;b__0()</d2p1:value>
</KeyValuePairOfstringanyType>
<KeyValuePairOfstringanyType>
<d2p1:key>ApiStepKey</d2p1:key>
<d2p1:value xmlns:d4p1="www.w3.org/.../XMLSchema" i:type="d4p1:string">5bda9bc3-4473-e711-8166-e0071b65e251</d2p1:value>
</KeyValuePairOfstringanyType>
<KeyValuePairOfstringanyType>
<d2p1:key>ApiDepthKey</d2p1:key>
<d2p1:value xmlns:d4p1="www.w3.org/.../XMLSchema" i:type="d4p1:string">1</d2p1:value>
</KeyValuePairOfstringanyType>
<KeyValuePairOfstringanyType>
<d2p1:key>ApiActivityIdKey</d2p1:key>
<d2p1:value xmlns:d4p1="www.w3.org/.../XMLSchema" i:type="d4p1:string">14d81039-bf63-464d-922f-674d5625b5dd</d2p1:value>
</KeyValuePairOfstringanyType>
<KeyValuePairOfstringanyType>
<d2p1:key>ApiPluginSolutionNameKey</d2p1:key>
<d2p1:value xmlns:d4p1="www.w3.org/.../XMLSchema" i:type="d4p1:string">System</d2p1:value>
</KeyValuePairOfstringanyType>
<KeyValuePairOfstringanyType>
<d2p1:key>ApiStepSolutionNameKey</d2p1:key>
<d2p1:value xmlns:d4p1="www.w3.org/.../XMLSchema" i:type="d4p1:string">System</d2p1:value>
</KeyValuePairOfstringanyType>
</ErrorDetails>
<Message>new_bpf_962fa5b399b048f59c8a425ed1c562d7 With Id = 00000000-0000-0000-0000-000000000000 Does Not Exist</Message>
<Timestamp>2019-02-08T00:45:18.8608222Z</Timestamp>
<ExceptionRetriable>false</ExceptionRetriable>
<ExceptionSource i:nil="true" />
<InnerFault i:nil="true" />
<OriginalException i:nil="true" />
<TraceText i:nil="true" />
</OrganizationServiceFault>