As far as I know I believe that we’ve fixed the problems that led to it appearing that list indexing sometimes started at 0 rather than 1. If you are still seeing this error, please let us know and, if possible, send us a share link to a project which displays the problem.
Please do not use the 'get property of object' block to do list indexing. The fact that that works is an artifact of our particular implementation of Lists that we might change in the future.
-Mark