Comment 2 for bug 1441455

Just curious: Why do you use path effects for all straight lines in that drawing?

If this is not intended, I'd recommend to check the current options of the pen tool (make sure that 'Shape' is 'None' and not 'From clipboard') - this will affect newly drawn paths only. For existing paths, you can remove unwanted path effects from selected objects via menu 'Path > Remove path effect' (to "fix" the behavior in this document).