When a user modifies a filter view, the cmn_attribute_value_sets gets populated.
If a custom filter created gets saved as default, then the specified filter is pushed as default when accessing that specific portlet.
If the filter gets corrupted, the system error is produced.
On these scenarios, please run the following select query:
SELECT * FROM cmn_attribute_value_sets
WHERE is_default =1
AND USER_id = 5001003 (id of the affected userid)
Check the result set:
We get one row with the following code: projmgr.odfKeyTaskList and ID 5016000
In order to overcome the error, the saved filter needs to be set as non default, so the user can then access the affected portlet and delete the corrupted filter.
That way, PPM will default to the OOTB filter and the portlet will not error.
This can be done with the following update query to the DB:
set is_default =1
where id = 5016000
AND USER_id = 5001003