I'm getting the same error except I'm upgrading from 12.3X48-D35 to D65 and using the ISSU feature for the cluster upgrade. Did you find a solution to this?
Not using ISSU and using the "no-validate" is not a good solution when dealing with production networks. If the config is not compatible it would be nice to know what it doesn't like.
In my case it was in regards to a service object that included a uuid of 000 000 00 000 or something like that, I didn't save the output. Either way I updated my config to remove that object and use the junos-ms-rpc object, removed the invalid object from the firewall completely and commited the change. Yet the upgrade still failed calling out the same error. I rebooted and have not tried again as I need to set another change window.