The mapping is date in both cases.
I tried to "force" mapping to "long" by creating the destination index manually, but then I get a different error (possibly still due to some bad data):
task encountered irrecoverable failure: Failed to execute phase [query], Partial shards failure; shardFailures {[61SMzV9PS5yHxMSjDcuhRw][pings-2017][0]: RemoteTransportException[[instance-0000000000][x.x.x.x.:xxxx][indices:data/read/search[phase/query]]]; nested: IllegalArgumentException[invalid value, expected string, got Long]; }; [invalid value, expected string, got Long]; nested: IllegalArgumentException[invalid value, expected string, got Long];; java.lang.IllegalArgumentException: invalid value, expected string, got Long