You can't attach bitmaps. Don't try it. Don't try to work around it. Bitmaps are bloated image files. Attach your images as .png files. If you want to embed the image within the post (and please not too large of an image that fills up the screen), the go back and edit your post. Right click on the attachment, pick properties and copy the file location as it points to the file on the NI website. Use the insert image button, go to the third tab. Paste the URL that you copied. Load file, Insert Image. OK.
(Snippets are done by way of the code capture tool.)
As for error wires. Yes it will enforce order of execution. A subVI can't run until all the inputs are available to it. That means the error wire as well. And there is no data on that error wire until the subVI upstream of it as completed.
