Upstream traceabillity error

If I try the upstream tracabillity option after having properly created several pickings with the correct production lot, I got this error under the web client:

Uncaught Error: QWeb2 - template['TreeView']: Runtime Error: TypeError: Cannot read property 'string' of undefined

In the gtk client, different problem: I just received the downstrem traceability panel even if I clicked on the upstream element. Moreover, there is no data displayed.

To test it with demo data:

1. Go into warehouse
2. [Create] a production lot in Traceability > Production lot on a specific product
3. [Create] an incoming shipment / delivery order with at least one line which is a movement of the product specified in point 2.
4. [Process] it and assign it a production lot
5. Go into Traceability > Production lot, open the corresponding production lot and have a look at the [Upstream traceability] button
6. here's the error.