Solve issue with webGL canvas alignment/scaling in Safari on iPhone when changing orientation

PLEASE READ THE ENTIRE DESCRIPTION BEFORE RESPONDING... We have a project using Phaser (using webGL). The page loads in landscape, and we have a rotate screen in there which shows up and tells the user to rotate back to landscape if they rotate to portrait. The problem is that when the device is rotated back to landscape in Safari on the iPhone, the content ends up being mis-aligned/scaled and showing a black bar across the top/bottom of the screen. We're assuming it's the canvas which Safari is setting inconsistently, so re-centering/scaling that correctly to the viewport size is what we think is needed, but we are open to any options to solve this. If you believe you can solve these issues, please let us know. We'll need you to sign an NDA then we can provide you with a version of the project for testing, along with screenshots and video of the issues happening, and answer any specific questions. When you replay to this please include the word "elephant" in your response so we know you have read the entire description, any responses without that will simply be ignored. Skills required: Please conform you have the knowledge and skills to solve this (html/css, javascript and experience with the quirks of iOS/Safari are essential, experience with multi platform web games/web apps across different platforms is essential, some experience with Phaser [login to view URL] specifically might be helpful but probably not essential. Deliverables: Updates to the project to solve the above issue, along with an explanation of what was changed for the fix. We'll also need to prove that the changes don't have any knock on effects causing errors on Android, iPhone Chrome, iPad, and desktop) We will test at our end on a range of devices and iOS versions to confirm. Note, we are only targetting iPhone7 upwards but the issues listed above only appear to be affecting more modern devices (iPhoneX up) Any questions please ask. Please prove that you have read and understood the project before bidding.