WordPress insists on changing certain characters into their & equivilants (when those characters appear within a code block) each time the article is udpated.  This wouldn’t be a problem except that the ampersand is one of the characters which gets this expansion.

If the article is always saved via the Text side this bug is circumnavigated.  This only appears to happen when clicking the Update button while viewing the Visual side in the editor.

This is how the problem increases with each subsequent save.

## 
Watch the ampersand go crazy:   "" >& 
""
&c… 
## 

## 
function func_error() {
    printf '%s\n' "[$( date +'%Y-%m-%d_%H:%M:%S%z' )]: $@" >&2
} 

if ! do_something; then
    err "Unable to do_something"
    exit "${error_did_nothing}"
fi 
## 

Just a fucking mess.

When I see that I’ve made this mistake (of click the Update button in an article with a code block while viewing the Visual side of the editor), if it’s one or two I just edit them directly and hit the update button from the Text side. If it’s a lot (I’m looking at you, “) then I pull the entire article from the Text side and paste that into VScode and make any find-and-replaces necessary.

The order is important here. First I change all amp;amp; into just amp;. Then I change all & into &. And finally I can fix each of the other expansions as required (usually <, >, and ").

Maybe this is fixed in a newer version? Could be. Have fun.