When a .md file cannot be loaded a message as its excerpt informs about the fact.
Added display of file content excerpts in case filenames are not informative enough, e.g.
Week 35--------+
2020-08-28 Fri | Drei Phasen der Softwareentwicklung (23 line(s))
2020-08-27 Thu | 2020-08-27 Thu / # Wahrscheinlichkeit einer Ansteckung au... (19 line(s))
...
The second filename consists mostly of digits and special chars. It's not telling much about the content of the file. Hence an excerpt was generated from its content (here: the first headline was extracted).