1) operating system - Windows 7 Pro
2) Evernote 6.22.3.8816 (308816) Public (CE Build ce-62.6.10954) and Firefox Browser 71.0
3) text only, but I don't use attachments, tables etc.
4) don't know where to see version of the editor, web client doesn't indicate anything except v5.27.1
In addition, I wrote previously that the problem dissappeares when deactivating laptop's touchpad. I found this tip somewhere cause had the same problem in Word 2010.