Exec OR begin...end;

Sometimes (and only sometimes) if issue an exec command like

exec procedure;

I get an ORA-01756 quoted string not properly terminated

copy the failing exec line to sqlplus and it will work so its something in the editor window. Any ideas?

To get it to work in TOAD I remove the exec and wrap a begin end around it (dont edit or touch the proc name)

begin
procedure;
end;

But just to repeat its only sometimes, I could repeat the same command with exec later on in a TOAD window and it will work.

To further complicate it , when I get the issue, this will work

execute procedure;

where
exec procedure;
fails.