Comment 4 for bug 1746052

Yes, the issue is result of overload.
Virtualized master node with storage shared with the other VMs/services has greater chance to encounter such issue.
High load creates a kind of disbalance between the master node block storage speed and other nodes. As a result - operation (save to DB), which in normal conditions goes faster then operations requested from the slave nodes, under load goes slower. So, the slave nodes may finish the tasks, send the results back to Nailgun and Nailgun requests to save the new operations results to save from DB, while already running transaction is still in progress. This is result of high parallelism level in Nailgun.

To reproduce it I use 4-core laptop with 16GB of RAM and 2 GB per VM, disk is SSD.
Fuel 9.2 (MU) deployment fully goes under VirtualBox.
In production this issue happens the same way, over the virtualized Fuel master node, with CPU pass-through.