Error in the template htm /usr/local/ispconfig/interface/web/client/templates/client_edit_limits.htm

Line 11 <fieldset class="inlineLabels"><legend>Limits</legend>

Change to

<fieldset class="inlineLabels"><legend><tmpl_var name="Limits"></legend>

Add string $wb['Limits'] = 'Limits';

to files translates /usr/local/ispconfig/interface/web/client/lib/lang/{lang}_client.lng