I have had the same problem as well many times. I purchased my Elite controller the day it launched. To date I have gone through 6 controllers with this issue among others.
The main issue is the Rubber, while most and even the Microsoft employees believe it is the glue holding the rubber to the plastic. I have seen now in all 6 of my controllers that it is not an issue of adhesive but of the rubber itself. After more than
30 mins of play anyone and every ones hands will get warm. It is this warmth that causes the rubbers makeup to expand. after 4-6 months you will first start to see signs of the warping issues on the outer rubber parts where a persons hand is usually always
touching (the other sides of the controller grips.
In the past I have gone back to the Microsoft store where I purchases my controller and shown them the issues where most but not all of the time they would give me a replacement. (note: they have also done this with my Microsoft Band 2 which suffered from
issues of the same type rubber, and also swapped out my plug and play charge cable and batter on different occasions.) However more recently I have had a the same issue with my controller in November of 2017 and the store I purchased the controller refused
to help me. I had to google this issue just ending up on Microsoft Xbox support live chat. After giving the serial number of the controller and such I was then given a case number and instructions to send in just the controller to the local warehouse Costing
me an additional $40 CAD to ship it.
In the end I shipped the controller Monday morning in December of 2017 and on Thursday I received a Box containing a whole new Elite controller with all accessories and now I have an extra case laying around. But it is now Mid March of 2018 and the latest
controller has already shown signs of a warp on the right top edge of the larger rubber. It is still usable and I feel the warp while playing but it is still comfortable for now however we all know this will not last long.
I have to ask Microsoft...
You marketed this as a durable controller tested by real gamers, How long did you let them test it for, 5 minutes?
What are you planning to do to solve this issue?
Why are you using such Unreliable and Cheap Rubber? Dense Memory Foam Might have worked better giving it a more padded feel and even a better grip.
Also I an unable to find evidence of this today but when announced there was to be a 1 year warranty on the controller this was part of the marketing behind the controller to show confidence in the controller durability. But now you go buy a new Elite controller
In a Microsoft Store and you are told it only has a ONE month warranty.