I got the “have some sync errors” message today. I right-clicked the icon and chose show file sync errors, and got this window.
I assume that it’s something about my system that made the text nearly invisible. I am running kde 5.17.2 on KDE Neon, which is basically just Ubuntu 18.04 with more recent versions of KDE. I haven’t noticed any other programs with unreadable text like this. Even other windows in the seafile agent are fine.