Same here as well as on all updated Iphones in my family. All 7 of them actually.
This definitely is a IOS bug, so please fix it ASAP.
All zeros typed after the first number after the decimal point are kind of kept in memory and all of them show up afer you type a number other than 0.
Would be just great if I could upload a short screen recording. It would be much simpler to explain, however only photos can be uploaded here.
Apple might want to make it possible as it’s much easier for everybody to address their issues.
Thnx