Canvas files, top and bottom cropped off in Chrome on ipad

My Animate for canvas is looking as intended on desktop, but on an ipad in Chrome, the top and bottom are getting cropped off. I am getting no console errors. My canvas is an interactive timeline with loads of popups etc. Everything works fine except for the ipad cropping issue.

I made a very simple test file, 1350 x 1000, to try and isolate the cause. Publish settings are pretty much at default, with "make responsive" and "center stage" ticked. Nothing tricky going on in the test file, no js, no interactivity, just a canvas with a couple of shapes in the corners, to check the crop.

As far as I can see this test file I made is about as basic as possible, but I still get the crop problem on ipad chrome.

Occasionally, if I keep reloading, or maybe do a few pinches, it seems to alter the amount of cropping. Once or twice it even looked ok. But by and large I seem to lose roughly 50px off both top and bottom.

It looks fine on ipad in FF or Safari, it's just in Chrome I get the problem.

I guess I just want to find out, is this a known issue with ipad and chrome, in which case there is nothing I can do about it,  or is it more likely that something about my files is wrong - maybe the publish settings?