I finally could reduce the undo stack size from the DConf editor, but this changed nothing. That's not the keyboard, as everything is fine from Nano. The workaround I'm using, is to use Komodo.
So far: it's not due to the undo stack, nor to syntax colouring, nor to line length, nor to file size, although any of these may have an effect, the behaviour occurs also without any of these.
I finally could reduce the undo stack size from the DConf editor, but this changed nothing. That's not the keyboard, as everything is fine from Nano. The workaround I'm using, is to use Komodo.
So far: it's not due to the undo stack, nor to syntax colouring, nor to line length, nor to file size, although any of these may have an effect, the behaviour occurs also without any of these.