Hi Mladen,

Indeed, there is still a load of open issues regarding TTL:

https://github.com/JanusGraph/janusgraph/issues?q=is%3Aissue+is%3Aopen+ttl

Your last remark about empty vertices sounds plausible, although it would be pretty bad if true. Searching on "new HashMap" on github gives too many results to inspect, so please keep an open eye on more hints where it would occur.
I did not see open issues that report empty vertices after ghost vertex removal.

Best wishes,    Marc