Some voltage sources seem now to have an "internal resistance". The output of theses sources drop when a load is applied.
1. Use 5V fixed volt., wave gen or Clock.
1. connect it to one 100 ohm resistor.
3. Put a probe/scope on the voltage source output.
4. 3.57 V instead of 5V on output of the voltage source is shown.
The sources "Rail.", "Volt. Source" and "Battery" are not affected. However also the op amp seems to be affected (can be checked applying a voltage follower).