Consider: we have request which is in Approval process and waiting for the Approval from Approver1. 

Now if Approver1 is absent, a new Approver (Approver2) should be able to re-assign the Approval ability to himself and should approve it.  But When Approver2 tried to update the ProcessInstanceWorkItem object to re-assign the Approval ability to himself (designed with a help of customisation), receiving an error as follows: 
“INSUFFICIENT_ACCESS_ON_CROSS_REFERENCE_ENTITY, insufficient access rights on cross-reference id: []”

Please help me to resolve this issue.

Consider: we have request which is in Approval process and waiting for the Approval from Approver1. 

Now if Approver1 is absent, a new Approver (Approver2) should be able to re-assign the Approval ability to himself and should approve it.  But When Approver2 tried to update the ProcessInstanceWorkItem object to re-assign the Approval ability to himself (designed with a help of customisation), receiving an error as follows: 
“INSUFFICIENT_ACCESS_ON_CROSS_REFERENCE_ENTITY, insufficient access rights on cross-reference id: []”

Please help me to resolve this issue.