If you have tried sending a keystroke combination with the "Send Keys" action, you may have noticed that if you click on the "Insert Modifier" button, and select for example the Shift modifier, WinAutomation automatically enters {Shift}() in the text to send field, and places the cursor between the two parentheses.

In order to send a specific letter along with the modifier, you will have to write something like this: {Shift}({W}) or {Shift}({C}) in the "Text to Send" field. This means that you will have to enclose the capital version of the letter in curly braces, inside the parentheses of the modifier.

Notice that the character inside the curly braces must be a capital letter, as it represents the actual character on the keyboard. Similarly, for the other modifiers: {Alt}({F}), {Control}({X}).
This is the advisable syntax to use the modifiers, and if you stick to it, your jobs will always work.