Many Searchable List Items Filter Function

Hello - 

I am working with the filter function to create a searchable list and am running into a problem where if I delete what was previously entered into a cell the dropdown continues to only had what was previously in the cell or "not found." If I try to update the cell and type in a different value I get data validation error (green triangle at top left of a cell). The cells in reference are in column B of the "stakeholder register" tab and are highlighted in yellow. 

https://1drv.ms/x/s!Amwn1Oi-aI1xdNY4Bjxi3_GR0_Q?e=8c5EOb

Thanks!