ERROR: [7502-21-223-80020009] Unable to get owner of GroupWise session
 Exception occurred.
Description: An error occurred in allocating memory.
ERROR: [434-21-223-80020009] Unable to get owner of GroupWise session
There may be corruption in Groupwise causing this problem as the error mentions a Memory allocation problem.
See this solution for details on GWCheck:
Try the following using the utility
i. Select the path to the post office and type in
the name of that same post office
ii. Select User/Resource and type the word “All” or a specific user in
the box below.
iii. Select Structural Rebuild from the pull down
iv. Click RUN
v. When that completes (NOTE: This step will be a
slow one), go back to the pull down and select
Analyze and Fix
vi. Deselect Structure, select Contents and Fix Problems
vii. Click RUN
Then try migrating again. You may have to run GWcheck multiple times to resolve this issue.