Lookup ERROR while trying to click on multiple visible elements on the page Helium/Selenium

I'd appreciate any help on this issue.

I'm trying to click (to expand) all years and months elements on this page:

<tbody ng-repeat="year">
   <tr class="year expandable title">
      <th colspan="6"><a>2020</a></th>
   </tr>
   <tr class="month expandable title ng-hide" data-month="1606780800000">
      <th scope="rowgroup" colspan="6">
         <a>
            <fin-date format="MMMM YYYY"><span class="display">December 2020</span></fin-date>
         </a>
      </th>
   </tr>
    
    <!-- [...] ALL OTHER MONTHS -->

   <tr class="month expandable title ng-hide last" data-month="1577836800000">
      <th scope="rowgroup" colspan="6">
         <a>
            <fin-date format="MMMM YYYY"><span class="display">January 2020</span></fin-date>
         </a>
      </th>
   </tr>
</tbody>
<tbody ng-repeat="year" class="last">
   <tr class="year expandable title last" aria-expanded="false">
      <th colspan="6"><a>2019</a></th>
   </tr>
   <tr class="month expandable title ng-hide" data-month="1575158400000">
      <th scope="rowgroup" colspan="6">
         <a>
            <fin-date format="MMMM YYYY"><span class="display">December 2019</span></fin-date>
         </a>
      </th>
   </tr>
   <tr class="month expandable title ng-hide last" data-month="1572566400000">
      <th scope="rowgroup" colspan="6">
         <a>
            <fin-date format="MMMM YYYY"><span class="display">November 2019</span></fin-date>
         </a>
      </th>
   </tr>
</tbody>

When trying this code below I always get a Lookup error.

for y in find_all(S('.year.expandable')):
  click(y)

for m in find_all(S('.month.expandable')):
  click(m)

Not sure why but it works If I click on just one element click(S('.year.expandable'))

Any idea what could be wrong?