it is for 11i and later.
there can be a corruption causing this.
Check accordingly.
Opening Forms After Clone Causes FRM-40735: ON-ERROR trigger Raised Unhandled Exception ORA-06508 (Doc ID 2247887.1)
Make a comparison between the source and target, compare the apps filesystem (relevant directories) and ensure there is no corruptions there.
If you can't find/fix it, we need more traces..
Obtain FRD (forms runtime diagnostic) trace.
Obtain truss/tusc on the forms web process
Also check the invalids! (Ref: Forms Login Fails With ORA-06508: PL/SQL: Could Not Find Program Unit Being Called: "APPS.FND_GLOBAL" (Doc ID 1598314.1))