[SOLVED] Today (02/20/19) update: problem with paragraphs and backwards delete key

[locksoft]

-- UPDATE --
Sorry guys, it seems it was an issue with my browser. After trying to reproduce the problem with another one (Safari), I restarted Firefox and now the issue is gone.

-- OLD TEXT --

Describe the bug
I've downloaded a new version of Gutenberg this morning. It's strange because it had no description about changes, just "last release" or a similar one. It appears to be version 5.1.0.
When I press the backwards delete button in a paragraph, the whole block is deleted.
It doesn't happens with all blocks. For example the CODE one works properly

To Reproduce
Just create a new paragraph, write some words and press the backwards delete key (it sould have a name, but english is not my main language, sorry, it's the big one above ENTER).

Expected behavior
Just delete the last char written

Screenshots

Desktop (please complete the following information):

• OS: MacOs High Sierra version 10.13.6
• Browser Firefox version 65.0.1

Smartphone (please complete the following information):

Additional context