before if i clicked on the number beside PROBLEMS I got a list with meaningfull error messages and when I clicked on a line i was led to the kine in the code where the error was dedected, Now I only get these long hard readable yellow lines where the error was detected.
A full clean also deletes the downloaded libraries located in the .pio/build/libdeps directory of the project.
However, since the libraries are specified in platformio.ini under lib_deps, they will be downloaded again during the next build automatically. There should no further errors occur after a full clean.