If a participant on a timing diagram has quite long name and its first activity is close to the diagram's left border then the label of the activity may overlap with participant's name:
See top left corner of the diagram only.
Thanks for pointing me to Plantuml webserver, it is very useful tool for providing issue details!
Here the link to reduced example of the overlapping:http://www.plantuml.com/plantuml/uml/SoWkIImgAStDuKhEpqlEB4vLK79sSGoETtCDSVQ8TmrpzGjHKaWiLa0NH2ZFIeet0Yi1CRYAanDpKXMC3K02XWO62WMP5QavnLmbcIL0OQ2UlDJaalmYlPpyT2u3XSnYXUgCp9IKrBnQBYu7T2iW2YmC5AmKKfAuj2qWwdL1IbFpKe1E1W00
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