Taking Care of Lex Bug

I know this has been mentioned before, but I’m stuck. The Stranger has been working on the forged letter for in-game weeks and he still says I’m bothering him. I can’t go back to a save before I gave him the letter. I’ve completed the Dark Brotherhood questline. I’ve tried most of every suggestion I’ve seen online. Is my only option at this point to finish the Thieves Guild questline in a new playthrough?

I doubt it will ever happen, but I hope they patch this.