AX 2012 R3 Upgrade Checklist Unable to Compile

We are upgrading from AX 2012 R3 CU8 to CU12. During the software upgrade checklist, we were able to complete the full compilation. When we reached the step of Full CIL, we got error & then when we tried to perform full compile again, we got the same error. This error also pops up when we compile any individual object in AX. Has anybody ever faced such error? Let me know if anyone has found a resolution to this.