as.h2o(data.frame/data.table) simply returns wrong data in special cases.
This is quite a bad one IMO as it just simply messes up the data silently. It seems like the issue is with reading from the temp file you write data to in the process of `as.h2o()`.
Here's a simple reprex:
The versions I have marked as affected are simply the only two versions I tested. And both have this bug.