I currently have the same issue, slight variation in our infrastructure.
We have four esxi 6.7 hosts fully patched. All hosts are connected to iscsi nimble san. Two hosts share majority of workload and iscsi connections. These are the only two hosts that experience the issue. I have managed to find a workaround at least in our setup. We have been restarting the vxpa and hostd services at least once a day if not twice And have not had the issue for 5 days. The services are restarted regardless of healthy host state.
Some of the logs reported “out of memory” errors and storage disconnects.