OS13.2 Gnucash 2.6.3 - Odd behaviour when marking cell items

I am experiancing an odd behaviour when I mark a cell.

Usually you would mark a cell with a double click or click into the cell and CTRL-A, then you could simply insert new entry over the old one by pressing SHIFT-INSERT or CTRL-V

But now at the moment if you select a cell and push the shift button the selected item gets unselected and you have to push CTRL-A again.

Or you want to enter a exchange rate and you cannot select the numbers any more and just type over, even CTRL-A DEL does not work right, you have to triple click in to the cell, then delete each value with DEL

That is freaking me out.

What was like 2 seconds entry before, if there was a repetetive value, with doublick - SHIFT-INSERT - Enter - ENTER- Doublick into exchangerate - entering EXC Rate - ALT-OK

takes now like 20 seconds. Really, really annoying.

Is this a feature or a bug?

At least the CSV import is now as fast as it should be. before 5 minutes for 10 values, now 1 sec.