can't find vmdk files while launching a VM

I am triggering three simultaneous requests via the rest api to launch 3 VMs. The first to get launched but the the third one says -

VMware ESX cannot find the virtual disk "/vmfs/volumes/59d7d966-0960271f-a9fd-f87588fbe35c/centos6.9-template/centos6.9-template-000006.vmdk". Verify the path is valid and try again.

If I try launching a VM for the same configurations, it works. What could be the issue??