fixed volatage property is not set

When trying to set voltage of Fixed Voltage Source the change in the Voltage value is ignored. Probably it is because QT signal is not connected for the widget. Therefore the property isn't set even when loading XML file , though the value in the file is saved correctly. The rail voltage source doesn't have this problem. This is in 0.5.16RC3

Yes, you are right.
Solved in Rev 222.