SoftMaker.com

I have recorded the problem in a video to demonstrate the problem.
https://www.youtube.com/watch?v=9nn_Z_SkS6s
As shown in the video, I can go on and keep typing forever, and all the undo does is registering one single "typing" action.
Once you click undo or ctrl+z, you will lose a huge part, if not ...

I am using (rev S1016.0624) 64bit on Windows 10 and I confirm the same bug.
I moved from Microsoft to Softmaker and found this software couldn't even get undo function right for a text processor. What a shame.
It doesn't apply for a particular document, bug is there even for a new document.
I have ...