Client Bills

I'm struggling to get the client bills to work.

I have a time & materials project with a resource allocated to it.
The project has an activity of type Task which is also assigned to the resource.
I've an Activity price which sets a price for the project/task combination

The project has been planned and the resource has entered some time into his timesheet for this activity.

If I create a client bill for this project and click on the add "formatted line" icon in the bill lines, then I get the bill line popup which allows me to select a resource, activity price, start date and endate. The price, quantity and amount fields are greyed out.

If I select my resource and activity price and a date range which spans the time period which has had time booked, the greyed out fields dont get filled in.

If I click on the OK button then I get the error message

SQLSTATE[25P02]: In failed sql transaction: 7 ERROR: current transaction is aborted, commands ignored until end of transaction block

The last error message from the error log is:
***** ERROR ***** [] Exception-[42703] SQLSTATE[42703]: Undefined column: 7 ERROR: column "2018-11-26" does not exist
LINE 1: ...e idProject='5' and idResource='13' and workDate>="2018-11-2...

I'm using a postgreSQL database and that's quite strict about quotes. If I replace the double quote in the above with a single quote then the query returns.