If you were to double click in the cell then press Enter key, does it fix the cell?
The reason why I’m asking is I see this alot where the data writes to Excel as strings and the green tick mark shows up. EDIT: and it gets fixed by editing the cell manually
You could try using the Workbook Write Range to see if there is a difference.
Also, are you using a Build Data Table? I wonder if you have the column set as String.
There are probably non-ideal workarounds like using Select Range, Copy, then Clear All, and Paste on top again.
Other than that, we would probably need a sample file to reproduce the issue and possibly find a solution.