Why is searching by one varchar column not working correctly on replica? PostgreSQL: 9.6, master, replica. 
Async replication, wal archiving. 

We detected that if we execute a select query on a varchar column against a replica, then the results return no rows, but if we execute against a master then the results will be correct.

SELECT id FROM platform WHERE name = 'test'



Master: 10
Replica: now rows




SELECT name FROM platform WHERE id = 10



Master: test
Replica: test




SELECT id FROM platform WHERE name in ('test', 'test1')



Master: 10, 11
Replica: 11




SELECT name FROM platform WHERE id in (10, 11)



Master: test, test1
Replica: test, test1


I didn't find any information about such issues and I don't know how to solve it.
As you say the column is indexed, try dropping and creating the index again. It might have gotten corrupted during replication.