I'm a software engineer who has been tasked with updating a client's C# macros which automatically generate SW parts and assemblies from their own in house software. The macros work more or less flawlessly with SW2019, but they want to now move to SW2025. There are some subtle differences in the way that SW25 executes commands that I have already fixed, as well as rewriting obsolete functions to bring them up to date. I am currently having issues with a particular part that is correctly defined in SW19, but has errors when running in 2025 after implementing a radius fillet between two perpendicular sketch lines.

This is the part of the sketch before the fillet

And after a 3mm radius fillet

The problem area highlighted is a short gap between the edge of the curve and the adjoining line

When selected, the following properties are displayed

In SW19, this gap does not appear and the sketch is defined correctly - what could be the cause here?