ODI-26211 "Mapping name is not unique" error — even with fresh repository and no agent

I'm working with Oracle Data Integrator 12.2.1.4.0, and I'm encountering a persistent repository-related issue. ❗ Problem: When I try to save changes to a mapping or generate a scenario, I receive the following errors:

ODI-26211: Mapping name is not unique  
ODI-20088: Error while generating the scenario  
ODI-10182: Uncategorized exception during repository access

This happens even though: It's a fresh repository. The mapping I created is the very first and only one. Tables such as SNP_POP, SNP_SCEN, and SNP_STEP are completely empty. 🔍 Additional context: Initially, I was able to save the mapping. Later, the error started appearing. I suspect this may have happened after I tried to run the mapping (it failed due to missing agent) — but I can't be sure. Renaming the mapping doesn't help. No agents are installed yet — I'm just using Standalone ODI Studio locally. 🔄 Environment: Oracle Data Integrator 12.2.1.4.0 (also tried 14.1.2.0.0 with same result) Oracle XE 21c, PDB: XEPDB1 Repositories freshly created Windows Server 2019 Standard No agent, just testing in local development 🛠️ Background: Originally I started in ODI 14c, encountered the same issue, then switched to 12c and recreated the repositories from scratch, but the issue persists in both versions. Any insight into what might be wrong with the repository setup? Could something be corrupted after running a mapping without agent? Any metadata cleanup suggestions?