Wikimedia Bugzilla is closed!

Intention:
I want to blank a page, and add new contents.

Steps to Reproduce:
Since this does not seem to happen on each page, I'll add the steps I followed to reproduce it.

1. VEdit https://it.wikipedia.org/wiki/Utente:Elitre_(WMF)/Sandbox_VE with Firefox and Monobook. 
2. Right-click, select all, delete.
3. Click to re-gain focus.
4. Type something. A pawn will appear.
5. Review your changes. Notice that not all of the contents were actually deleted after #2. Also notice that some or all of your newly added text might be missing. 
6. Save the page. Your text (most or all of it) shouldn't be there. What you have are random chunks of old text. And your pawn :)



Actual Results:  
While reproducing, the following also occurred to me:
1. After blanking, a weird cursor (like an arrow pointing up) appeared at the beginning of the line. After typing for a while, Back Space and the keyboard navigation arrows wouldn't work. 
2. When VEditing the page created after #6, blanking it and then clicking on a line to make the cursor appear resulted in fragments of words appearing. If I tried to type, I'd also get rapidly multiplying pawns.
(All these behaviors are not new to me.)   

Expected Results:  
I expected the page to be really blank, and pawn-less :)

Reproducible: Sometimes