Here is one H815 international version with the stock 5.1 rom in it. I too have touch screen unresponsiveness as a problem with my device, I've owned the device for just over a week now, previously have had Samsung devices, latest was Note 3. None of them had _any_ issues regarding the responsiveness of the screen, and so far I've thought that this is just a feature of an LG device. But alas, it seems it just seems that it is the LG G4 that IS the problem.
- double tap wake doesn't register easily, you have to double tap several times
- while typing, you get really bad lag and miss letters if you write too fast with the device. This is ridiculous as it's a 2015 device, and was (still is?) the flagship of LG. Again, I had no issues with Samsung devices that I've had (i9000, i91000, i9300, GT-N7100, SM-N9005).
- I also did the factory screen test that pops up with the specific code, and on the edges the touch recognition is very bad. You have to glide your finger very slow and careful on the edge and most likely even then the screen won't recognize the touch.
This makes the device a pain to use. Wish I had not fallen through ice 2 weeks ago, I would have my Note 3 still functioning. :s