This is the subject of a bug report but not liable to be fixed soon. (this one https://gitlab.gnome.org/GNOME/gimp/issues/2295 )
What you might have is this: check this screenshot: https://i.imgur.com/AUhmyJy.jpg top to bottom
The '9' size 28 px colour red. text tool properties (global) 18 px black. The text cursor is to the right of the nine.
Move the text cursor to the left of the '9' and the properties in the on-canvas text is how you started 18 px black.
Delete the '9' and that leaves anything typed as 18 px black.
The workaround, if that is what you can call it, is keep the cursor away from that starting position.
screenshots: https://i.imgur.com/u7WoPib.jpg
Put the cursor to the right of the 9, properties 28 px red, type in a 4 still 28 px red.
Move the cursor to between 9 and 4
Delete the 9 ( move the cursor back to right if you want).
You hit on the one instance where this is particularly noticeable, a single character. Replace a character in the middle of some text and there is no problem.
What you might have is this: check this screenshot: https://i.imgur.com/AUhmyJy.jpg top to bottom
The '9' size 28 px colour red. text tool properties (global) 18 px black. The text cursor is to the right of the nine.
Move the text cursor to the left of the '9' and the properties in the on-canvas text is how you started 18 px black.
Delete the '9' and that leaves anything typed as 18 px black.
The workaround, if that is what you can call it, is keep the cursor away from that starting position.
screenshots: https://i.imgur.com/u7WoPib.jpg
Put the cursor to the right of the 9, properties 28 px red, type in a 4 still 28 px red.
Move the cursor to between 9 and 4
Delete the 9 ( move the cursor back to right if you want).
You hit on the one instance where this is particularly noticeable, a single character. Replace a character in the middle of some text and there is no problem.