Homemade, sorry to say - but these waypoints (USR, Rxxx, …) comes from the sim and are not included in our database. Also, when you add approaches to a STAR, that some waypoints will be truncated, the flightpath doesn´t match the real-path (ie. on the charts) and so on … we and also you can´t do anything only to wait, if and when Asobo will fix it. This is a confirmed limitation by Asobo/MS and is navdata independent.
What you can try is, to use the Working-Title CJ4. This mod doesn´t use the internal flightmanagement logic of the sim. They had developed a own one and this works nearly perfect - independent which data you´re using. Worth to try … you will see a hug different …
Cheers,
Richard