Issue reading file in a thread

We are using file_search and have a thread (id: thread_3RC5ow6MLE612fn4ZsuzhUVU) where the assistant is constantly excusing itself that it cannot read the files that were uploaded. There is just one file there, which seems to work just fine if we upload it to another thread (like in thread_BjrL37jMwuM8gY8GZgdSc9fX).

Could someone shed some light about what happened in the thread first mentioned here? Is there any way to know what happened there and a way to prevent it or resolving whatever went wrong?

Related to this. Another issue we have seen is that sometimes the assistant says there are no files, even if one is added to the thread. The files can be seen in the UI of OpenAI by inspecting the vector store. An example of this is the thread with id thread_F4PDlqXDh37UbinToLhPUnjI.

What can we do in cases like this? Like before, is there any way of preventing or at least detecting and fixing these issues?