I can't see history for my temperature sensors

Hi,
I have enabled debug log and i see :

2018-06-19 12:52:48 ERROR (Recorder) [homeassistant.components.recorder.util] Error executing query: Object of type ‘Element’ is not JSON serializable

How can i find out which component or what’s causing this ? No more info is in the log that points to the culprint.

I am running 0.71.0, i have tried to delete the db file but the problem comes back.

/donnib

Nobody has an idea ?