There may be times in which Lottie doesn't render your animation correctly. After effects has an enormous number of features, not all of which are supported by Lottie. If an animation doesn't look correct, run through the following steps before reporting an issue.
The Lottie for Android will automatically detect and report some errors. It doesn't catch everything but will catch many common cases. You can either call
getWarnings() from your own code or open the animation in the Lottie sample app and see if warnings show up in the top right. If they do, tapping it will give you more information.
Check the supported features page on this site to see if you are using anything that isn't supported.
Try rendering individual parts of the animation to see which feature isn't rendering correctly. See if you can narrow it down to a specific combination of shapes and effects or anything more specific than "it doesn't look right". If the issue should be supported and isn't, file an issue on the appropriate lottie github page with a description and a zip of the aep file.
Merge paths are only available on KitKat and above so you must manually enable them.
Make sure you are using the latest version of Lottie.