Troubleshooting Device ID Change During Domain Transition

I am using Simplified ID Merge in my project. My main domain is https://digitalartifact.ai/. When I visit the site, a device ID is generated. At this point, the user is not authenticated. Users navigate from the main domain to the subdomain https://app.digitalartifact.ai/, where they get authenticated. However, during this navigation, the device ID changes, causing events not to merge. What can be done in this scenario?