Re: "not in a transaction", but only sometimes

Forgot to mention: Fuseki 3.12, and this is the error [2019-09-10 17:02:32] QueryIteratorCheck WARN Open iterator: TripleMapper/255 [2019-09-10 17:02:32] Fuseki WARN [7] RC = 500 : Not in a transaction org.apache.jena.tdb.transaction.TDBTransactionException: Not in a transaction at

"not in a transaction", but only sometimes

Just out of curiosity, has someone else here experienced a query that returns "not in a transaction" only sometimes? I have a simple dataset like this :dataset a ja:RDFDataset ; ja:defaultGraph :union :union a ja:UnionModel ; ja:subModel :graph1 #TDB ja:subModel