I had a mild propane smell for quite awhile. Plus, whenever I shut the propane off for a day and then turned it back on the lines would already be empty and need bleeding. After quite a bit of sniffing around (Both figurative and actually) I discovered the regulator for the stove burners was leaking just a bit. I replaced it, the smell went away and now I can go for a week or more without needing to bleed the lines after I shut the gas off.
Use your nose as a detection device and see if you can find where the smell is coming from