Backspace erasing text itself by the inertia

One click on the key Backspace initialized erase slow one by one ten or more symbols. I hear how works HDD. What I need to do?

i7 4770 3,4 GHz, 4*2 DDR3, SDD128, HDD1TB
Mint Cinnamon 20, LibreOffice 7

Troubles starts from LO6,4.

If i use Backspace in simple editor *.txt phenomenon not repeat.

To get any decent answer, edit your question to add OS name and LO version. Is your hardware recent? It is always possible to install up-to-date OS and applications on vintage hardware to the price of slow reaction (I still have a 650-MHz Pentium III running a 6-years old Linux distro and LO; I don’t dare to upgrade because I’d have to recompile everything for 32-bit).

In Windows go to Control Panel > Keyboard > Speed and slow the Repeat rate.

But if it is Windows is it up-to-date? I recall something like this a while ago, maybe a year, it occurred in several programs, including Thunderbird. It went away after some Windows update or another.