After the bugfix I found another problem that the "default" skinparam of an arrow is not supported too.
E.g. if the default style of an arrow is green and only parts of the styles are overlayed via skinparams then the line should not be invisible/white (in older versions the final combinations orange/green or green/orange were working)
@startuml
skinparam arrow {
Color green
FontColor green
}
skinparam arrow<<orangeText>> {
Color ;text:orange;line.dotted
}
skinparam arrow<<orangeLine>> {
Color orange;line.dashed
}
skinparam arrow<<origGreen>> {
Color ;line.dashed
}
rectangle "==A" <<person>> as a
rectangle "==S" <<system>> as s
rectangle "==E" <<external_system>> as e
a -->> s <<orangeText>> : **orange text**
s -->> e <<orangeLine>> : **orange line**
a -->> e <<origGreen>> : **origGreen**
@enduml

BR Helmut