Hi, Chad--You are ahead of me, but I have had a similar experience. I would miss an attempt at a given weight, then repeat it the next week. Early on, I would often get the lift for at least 3 reps or even 5. Then the next week, I would add 5 lbs and see how many reps I could get. When 5s no longer worked, I would go to 3s, which would continue for a few weeks with 5 lbs jumps, and then to 2s and then finally to singles (I would just pull one and then do back offs). Most recently I pulled 405 for a single and then the next week (last Saturday) I missed 410. I will try to repeat it this week (maybe even try 2 or 3 singles, as you are doing). Whenever, I stall out--can't get the single two or three weeks in a row--I will cut the weight back to slightly above where I last was able to do 5 reps, and start over with 5s, then 3s, etc.
Sometimes I think that the issue with my difficulties hitting my DL target each week is just one of frequency and recovery. I am not that experienced a lifter, but my thinking was that when my current approach failed to yield improvement, I would try to avoid heavy DLs every week, and substitute them for some rotation of RDLs, Rack Pulls (both of which I am doing now), deficit deads, shrugs, good mornings, dynamic effort DLs, or whatever else might assist. I would then pull heavy every second or third week. I am not sure if this is the most productive, and am open to any other more effective approaches. I am very interested in hearing what other lifters do in this situation. Thanks for starting this thread.