tgf falls out of input (in a Tag field) at window change

[hopalongrock]

If I return to the field in the Tag grid, I have to go input again and position the the cursor, to enter characters to the proper place, and  don't clear the original text with the newly inserted text. There is no such problem in Manual Edit.
This occurs too, when I use a program to insert some text at a cursor position.

If there is no option to handle this, please make one, or change this behavior (retain cursor position).