Why does the keyboard duplicate the previous character?

Question

Keyboard

Good day! I work with wireless keyboards connected to a laptop. I began to notice that when typing fast, some letters are duplicated. Moreover, this does not look like the effect of sticky characters, I have already reviewed all possible system settings, increased and decreased the delay before repeating, specifically turned sticky keys on and off, eventually returned the system settings to default again, but the problem persists.
Moreover, this does not happen on the keyboard built into the laptop.
It is on external wireless keyboards:

• Sven Comfort 3500 Wireless (USB receiver)
  
• Zoweetek ZW-51012BT-1 (Bluetooth)
  

The problem is not observed for all words. But, if I do not focus on them and type quickly, then this is repeated regularly. An example of such words:

• flowing to _
  
• application and
  
• expose t
  

I deliberately slowed down and paid attention to how I type characters - I definitely don’t press these letters again. I just type them in sequence and release the keys in the same sequence.
System: Windows 10.1 Version 1903 Build 18362.388
All updates applied.
I also sinned on Punto Switcher, but the problem also appears after it is turned off.