Visibility return 99999 whne performed on high radius

[mody_buchbinder]

I am running Visibility on a 1 Meter DTM (UTM projection).

Using a radius of 30000 return 99999 after about 1:30 minute.

Running on 20000 meter (all other parameters are the same) return good results after a little over 10 minutes.

Pro 3.2, no memory problem on the machine.

Anybody have any idea?

Thanks