Salesforce - Error to push new version into an Org due Encrypt Field

This week, we got an error to upgrade a new version into a customer org. The error shows that we didn't have kind of access to LastName field, but I could not duplicate the issue if I removed access in that table.

 "classes/XController.cls SELECT Id FROM Contact WHERE LastName = 'X 1' limit 1 ^ ERROR at Row:1:Column:30 field 'LastName' can not be filtered in a query call classes/XController.cls SELECT Id FROM Contact WHERE LastName = 'X 1' limit 1 ^ ERROR at Row:1:Column:30 field 'LastName' can not be filtered in a query call classes/X.cls SELECT Id FROM Contact WHERE LastName = 'test 1' limit 1 ^ ERROR at Row:1:Column:30 field 'LastName' can not be filtered in a query call classes/X.cls SELECT Id FROM Contact WHERE LastName = 'test 0' limit 1 ^ ERROR at Row:1:Column:30 field 'LastName' can not be filtered in a query call"


First I did some research and I found this Forum which I thought could be something related with encryption. In the end I contacted Salesforce and they said the customer has marked the field to encrypt and then unmarked the field, when it happens the customer should contact Salesforce so then can run a "historical data decrypt", because the customer didn't contact SF, we got into this issue. After they run that we could upgrade the customer.