A large number of records in ODF_ITEM_POSITIONS table can cause severe slowness with projects updates, task deletion and delete investment job.
Looking in ODF_ITEM_POSITIONS by count, you see a large number of records on projects::tasks, on a single project.
The application performance degrades, due to the increase in picklist item position records.
Release : 15.9.3, 16.0, 16.0.1
This is caused by DE63987, fixed in 16.0.2 and it is patched on 184.108.40.206