Eden, this is a continuing thread from the last forum.  I logged on to see any updates and found there's now a new forum.  Was there anything resolved with this issue?

When typing in notes in a new or existing entry, after the third line of the note, all the notes disappear from the screen.  If saved, they are recorded in the entry.  If edited past the third line, they disappear again.

Video is here:

 https://www.dropbox.com/s/rbu8egj7vawczz6/IMG_0191.m4v

Hi Dave,

I think I remember your post on our previous forum. Unfortunately, or fortunately, I cannot recreate your issue here. 

Can you tell me more about your Mac? 

1. macOS version
2. Type of Mac
3. Processor
4. Memory
5. Video Card

This happening to my Mac too.  

MacBook Pro (Retina, 13-inch, Early 2015)

Processor: 3.1 GHz Intel Core i7

Memory: 16 GB 1867 MHz DDR3

Graphics:  Intel Iris Graphics 6100 1536 MB

OS X El Capitan

I did your steps above, but I'm still having the issue.  Once I enter a note on line 4, the whole note disappears.  If I place my cursor in the password field, press tab once, then Select All (Command + A), then Copy.  I can paste the contents from the clipboard into my notes app.  So the data is there, I just can't see it when editing a "Login" entry.  After I save the entry, I can see the notes displayed just fine.  As a work around, I enter my notes in another editor, then copy/paste them into the note field.

Upgrading to High Sierra also remedied this situation for me.