I am not having any issues when I draw my own freehand splines.
However it is very easy to create loops and double nodes, so maybe that is an issue.
The magic wand may be having a hard time figuring out which nodes to follow.
Try using the magic wand to 'flood' the internal area, rather than clicking on the perimeter, to see if that makes any difference.
Or click on the perimeter if you are already flooding the area.
As I was playing around I just had a 'wait' cursor for about 20 seconds and then I could keep working.
I pressed undo and tried again with no problems.
Tried again 10 second wait.
Tried again no problems, and again no problems.
Tried one more time and now Archicad is frozen and I will have to force quit.
So maybe there is a bug there somewhere.
One of the forum moderators.
Versions 6.5 to 25
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10