Adding letter infront of the text --> makes it BOLD, not regular

Hey Community, recently I noticed very annoying thing.. If I have text, for example Poppins Regular  in illustrator and I need to add any new word / letter in that  existing text - it's formating becomes BOLD, not Regular.

Before I didn't had any issue, I didnt even changed anythign in the settings.. It accures on both systems MAC & Windows.. Is anyone aware how to solve this? ;( Thanks!