This problem does not happen all the time only towards the end of some designs. I get hidden edges appearing as guide lines in my model. The only way to get rid of them is to cut and paste into a new file and save as a different name. I have uploaded the file photo so you can understand what I mean
Try hitting k on the keyboard.
What you see / mention are just ‘Backedges’ of your model. In face style there is a button somewhere next to the X-ray face style button to toggle these back edges on and off. Probably the shortcut key that @Box has mentioned.