The updates to the mobile style can remove the editor from your default style if vBulletin is improperly configured.
In your Admin CP go to Settings -> Options -> Style and Language Options.
Set Default Style For Modern Mobile Browser to None.
Set Default Style For Old Mobile Browser to None.
Save at the bottom.
Always make sure your default style is not set as mobile in style. Modern/Old Mobile styles should have either none or your mobile style selected; not desktop style.
In your Admin CP go to Settings -> Options -> Style and Language Options.
Set Default Style For Modern Mobile Browser to None.
Set Default Style For Old Mobile Browser to None.
Save at the bottom.
Always make sure your default style is not set as mobile in style. Modern/Old Mobile styles should have either none or your mobile style selected; not desktop style.