1. Siquence diagrams are failing on messages which are on one line ao more than 901 characters (even if it's splitted with \n)
2. Following the hint from https://forum.plantuml.net/3104/sequence-diagram-messages-on-multiple-lines
Splitting the line with "\" it helps a bit, but if the complete line (including those merged by "\") eceeds 2013 characters, the participants are automaticaly tranformed into classes and the text is justified aligned.