Currently the compiler is not double precision compliant but you can still use all the double types (double16 included). Basically that just means that from between now and when the compiler is double precision compliant you *may* see small variations in the results, which is similar to what you sometimes see when porting code between different CPU archetictures.
Double check the version that you are using, you may be running into a known bug that has already been fixed. You can check the version by running "aoc --version". The latest version is 13.1.4 which is 13.1 with update 4 installed. There is a sticky post at the top of this forum about the updates and where to go to download them.