After upgrading application from Pega 6.2 to Pega 7.2.2 version, getting error while opening assignment from workbasket display error screen is coming loading pzharnessfailmain and incomplete data is coming for few tabs if we try to search the assignment as well. Pega pzChecklockingMode activity obj-open-by-handle is getting failed and this activity was not present in Pega 6 version, this activity is getting called from OpenAndLockWork activity. pzCheckLockingMode activty is getting failed error message in tracer "The reference [not specified] is not valid. Reason: null reference". But this issue is happening only for existing assignments, for new assignment we are able to open and search the assignment and its working for newly created assignments.
***Updated by moderator: Lochan to add Categories***