In old version stereotypes/skinparams with spaces in the name were correct displayed
BR Helmut
@startuml
skinparam rectangle<<backend container>> {
StereotypeFontColor #FFFFFF
FontColor #FFFFFF
BackgroundColor #335DA5
RoundCorner 0
DiagonalCorner 18
}
skinparam rectangle<<backend_container>> {
StereotypeFontColor #FFFFFF
FontColor #FFFFFF
BackgroundColor #335DA5
RoundCorner 0
DiagonalCorner 18
}
rectangle "Backend with space in stereotype name" <<backend container>> as c1
rectangle "Backend_with_underscore_in_stereotype_name" <<backend_container>> as c2
@enduml