Problem solved. I downloaded VMware vCenter Server 7.0U3h, I was able to perform the upgrade.
What is your VCSA 6.5 build version?
For testing purposes try to upgrade to VCSA 6.7 and to VCSA 7.0.3 after that. Maybe there are some bugs in your build.
I did the path VCSA_65 >>>> VCSA_67, it worked.
Then I tried VCSA_67 >>>> VCSA_7, it gave the same error "Internal error occurs during Export of Vmware vSphere Update Manager"
Difficult !
Problem solved. I downloaded VMware vCenter Server 7.0U3h, I was able to perform the upgrade.