Hey, I think I fixed your problem!
First of all, the map looks really beautiful. I wish I could play it but I cannot because it looks like this for me
View attachment 514356
Anyway, I saw some weird things, like a wasteland named "Silk Road", and other provinces having the names of vanilla provinces, like you described. This is caused by your province names (PROV123 etcetera) being overwritten by original province names.
That is because the game sees PROV123 etcetera twice: your version, and the original version. They are both in the localisation csv files. Then the game picks one randomly. That is why some provinces were given the original names and some were given your names.
The solution is to rename your file, provinces_and_titles.csv, to 00_provinces_and_titles.csv. The two zeroes in front mean that it will be read first, and the name read first wins. So change the name of provinces_and_titles.csv to 00_provinces_and_titles.csv and every province will have the proper name.
Please tell me if that solved what you asked about