I’d suggest treating them each as a movie and giving them names like “Health Congress Part A.mkv, Health Congress Part B.mkv, etc” then using the xml file sample in the users guide here
to create a file for each. You could even do the custom artwork for each by naming the posters as stipulated in the above Users Guide. For example name the poster you want for the first one “Health Congress Part A.jpg” and so on.
You may have some characters in the file name and in the xml file that are confusing for the system and Infuse. Characters like the ampersand “&” can cause problems at times.
Instead of “Stress & Relax Festival Tag 1-1 Dr. Alexander Hierl”
Try changing the file name and the xml file “title” to
“Stress And Relax Festival Tag 1-1 Dr Alexander Hierl”