I am having the same duplicate issue (only on mobile) and only one 1 of my 4 vehicles stored.
I miss the old Gas Cubby.
Also, it's a huge negative that you guys got rid of the search function. Search is VERY useful. For example, if i want to find every service entry that i did a brake job on my car, i can simply search keywords instead of scrolling through all of my service entries looking for the one i want.
When i was updating my service reminders after the update, i was trying to search how often and the last time i did X jobs and i instantly gave up because there was no quick and easy way to figure it out.
OK i had to log out (then it froze on the sign in screen), i had to kill the app again, then when i opened the app again, i was already signed in and all my duplicates were gone (both Fuel Ups and Services). I hope my notes can help others who are having the same issues.