The latest version of ETA is 3.3.0.L1 in the Elektron SDK C/CPP 1.3.0.L1 package. However, I am unable to find any known issues regarding the duplicate stream IDs for Symbol List in the CHANGELOG file.
For now, it is better to upgrade the application to ETA 3.3.0.L1 and if the problem still happens with ETA 3.3.0.L1, you can submit this issue via Contact Premium Support at https://developers.refinitiv.com/elektron/elektron-sdk-cc. Then, the API support team will investigate the problem.
You can download the Elektron SDK C/CPP 1.3.0.L1 package at https://developers.refinitiv.com/elektron/elektron-sdk-cc/downloads.