Mass delete may have you delete unwanted records?

Mass delete may have you delete unwanted records?

We recently imported around 20k contacts into Zoho CRM from a CSV-file generated by Salesforce. Around 4k of those had a field 'ISDELETED' that indicated whether those contacts were deleted in Salesforce. We mapped this field to a new field in Zoho in order to be able to delete them later on.

Afterwards, I attempted to use the Mass Delete functionality where I used this field to filter the results. After browsing to the last page of results, I checked all contacts to delete and deleted them. The page reloaded and was filled with contacts, once again, while the number of results remained the same. This can't be true if the 100 selected leads were deleted, of course. A check on these results showed me that these newly discovered leads in fact did not have the deleted marker. Apparently, when refilling the last page, the filter is ignored. This makes it quite easy to accidentally remove leads that do not match the selected criteria. I actually did, and had to undo the import because the list was in an unknown state.

Is this a bug or did I do something wrong?