InDesign v19.5: Data Merge Problems with Diacritical

I wanted to use "Data Merge" again after a while, but I found that it no longer works as it did in the previous version (v18). In the old version (v18), "Data Merge" worked correctly with diacritics, but in the current version (v19.5), it does not, and it's definitely not a font issue (I’ve tried all of them). The ".csv" file is exactly the same as the one used before, and when I use the old version, everything works as it should. The problem occurs with certain characters, such as "Š", "Č" and "Ř," which are used in my language, Czech. The CSV is exported from Excel (MS Office).

I have not modified any preferences or settings in InDesign; everything is set to the default.