Version Store usage and entries in dm_tran_active_snapshot_database_transactions

So I'm trying to understand why are having occasional problems with tempdb filling up with version store entries. I'm closing in on the problem, and am now seeing entries in dm_tran_active_snapshot_database_transactions, but I don't understand why the entries are there. The databases in question do not have ALLOW_SNAPSHOT_ISOLATION or READ_COMMITTED_SNAPSHOT enabled. Checking the transaction via dm_tran_active_transactions I can see the following properties:

`
transaction_begin_time (90 minutes ago)
transaction_type 1
transaction_state 2
transaction_status 0
transaction_status2 258
dtc_state 0
dtc_status 0
dts_isolation_level -1

` Any ideas how to troubleshoot this in a methodical manner?