These internal documents, obtained by Motherboard, were part of a class-action lawsuit filed against Apple. However some of them were made public by US District Court Judge Lucy Koh in a recent opinion in the case, and based on the information that was made public, it appears that Apple was aware that the iPhone 6 was prone to bending.
The document reads that Apple’s internal testing discovered that the iPhone 6 was 3.3 times more likely to bend compared to its direct predecessor, the iPhone 5s. This was worse with the iPhone 6 Plus which was found to be 7.2 times more likely to bend, presumably due to it being larger.
It is also because that it is prone to bending that caused the “touch disease” where the phone’s touchscreen would suddenly stop working. However according to Koh, it was only in 2016 that Apple had quietly begun to reinforce part of the logic board that might have caused the problems.