I think this is likely because though the pbf size is small for south america, the geographical context is a lot bigger so there is quite a bit of elevation data that would be loaded aswell. The bit that it is failing on is in the landmark processing, and so what I expect is happening is that because the number of threads for preparing is set to 8, having both shortest and fastest calculations happening at the same time is too much. Try doing it again but in the following:
"lm":{
"enabled":true,
"threads":8,
"weightings":"fastest,shortest",
"landmarks":24
}
change "threads": 8, to be "threads": 1,