Hi Arsenico,
Quoted from another similar post at https://learn.microsoft.com/en-us/answers/questions/544305/tf400898-an-internal-error-occurred
TFS is now Azure DevOps Server so you'll want to speak with DevOps specialists using the link below. My understanding is that error can mean a couple things from request timeouts (there may be a temporary issue with the service) or even full storage.
The Azure DevOps team and DevOps community are actively answering questions here:
https://developercommunity.visualstudio.com/spaces/21/index.html
If this is helpful please accept answer.