"Error while trying to add Ext Ref field in ChaRM CR form by using personalized settings"

Hi Experts,

I have got the below error when I tried to add the External Reference field in the ChaRM CR form in Request for Change. I have already used one external reference field for adding incident but when I tried to add the same field in the project planning section and save it to a transport request. When I try to open the form using SM_CRM I got the below error: Please help