The reason for single row editing is that when updating the Cell extjs re-applies HTML attributes to the cell.

This cell of the Checkbox Field looks like this.
<span (tickets.alltickets.closed)="" whether="" this="" investment="" is="" closed,="" i.e.="" certain="" things="" should="" not="" change="" anymore.="" class="x-grid-checkcolumn x-grid-checkcolumn-checked" role="button" tabindex="-1" id="ext-element-34" data-tabindex-value="0" data-tabindex-counter="1"></span>

The Tooltip and help text for that colume is:
(tickets.alltickets.closed) Whether this investment is closed, i.e. certain things should not change anymore.

The first attribute is raising InvalidCharacterError: String contains an invalid character.

This is very strange behavior.