In map-view.ios.js the mapViewMarkerInfoContents function calls tns-core-modules/ui/utils ios._layoutRootView which does not exist in tns anymore as of pull request #7382 on June 25. I don't know whether this breaks all info windows or just custom ones, but it's throwing this error and crashing the app.
JavaScript error:
file:///node_modules/nativescript-google-maps-sdk/map-view.js:164:30 JS ERROR TypeError: webpack_require("../node_modules/tns-core-modules/ui/utils.js").ios._layoutRootView is not a function. (In 'webpack_require("../node_modules/tns-core-modules/ui/utils.js").ios._layoutRootView(content, CGRectMake(0, 0, width, height))', 'webpack_require("../node_modules/tns-core-modules/ui/utils.js").ios._layoutRootView' is undefined)