If your items have batches traceability and the message Odoo Server Error  present in the title of the movements of the inventory you should:

1. Access to Inventory > General View 
2. Click the 3 dots in the right upper corner from the box and select Configurations
3. Select the option Use existing batch/serials numbers

To get valued reports you have to upload items with their cost price

1. Open the desired item
2. Click in Edit
3. Add the cost price in the Cost Field
4. Click in Save