They are on different index sets. All Messages stream is on the Default index set where our custom stream is on a new index set that we created. However I checked both index sets and they are configured the exact same way (ie. shards #, replicas #, rotation strategy, rotation period, etc.) they are identical.
You gave me an idea though - since the index sets are identical, I switched my custom stream to use the Default index set and everything works perfectly. But I need to be able to create custom indexes and have them working vs dumping everything into Default. And other question is why is the indexing/parsing of timestamp different on two index sets that are identical in configuration?
UPDATE: Based on the above I thought maybe it was an issue specific to my index set that I created. I created a brand new index set and migrated the stream to it and it seems to be working. I still can’t explain what is wrong with the first index set I created, but new one seems to be indexing without issue.