Hello A.,
For more precision, in fact that generates on error only if that is on several line.
But if we use '\n' on one line that is good:
One-line: OK
@startuml
while (condition\non several lines) is (yes)
:my activity;
endwhile (no)
@enduml
Multi-line: KO
@startuml
while (condition
on several lines) is (yes)
:my activity;
endwhile (no)
@enduml
If that can help,
Regards,
Th.