Weird extra lines when using extensions on class diagrams and groupInheritance

Question

Hello, 

I am new to PUML (and UML in general) and have found an issue. When using groupInheritance, extensions (<|-) cause the item they are "pointing to" to partially show hidden lines. I do not know if this is a bug or intended, but decided to post it here. The issue is replicated in the example below. The connection between "A" and "B" should be invisible, but because 'A' is using `<|--` and not `<--` for other connections, a partial line going to nowhere is shown coming from it. 

Replication example: 

@startuml A <|-- AA A <|-- AB A <|-- AC A <|-- AD B <-- BA B <-- BB A -[#Red,hidden]left- B skinparam groupInheritance 2 @enduml

ex 2 from duplicate: 

@startuml C<|-left[hidden]->B C<-left[hidden]-|>B A<-left[hidden]-|>B skinparam groupInheritance 2 @enduml

Comments

When using:

@startuml
A <-- AA
A <-- AB
A <|-- AC
A <|-- AD
B <-- BA
B <-- BB
A -[#red]left- B
skinparam groupInheritance 2
@enduml

one should look at the lines between A and AA and A and AB and especially note the place of the arrow head there

---

And also should note the coloring between A and B