One of my papers was submitted in Springer journal on 16th July 2023. After two months later, the status changed to "UNDER REVIEW" on 19th Sept. 2023. The status changed to "UNDER REVIEW" twice again on 15th May 2024, 19th May 2024 this year.
What does it mean? I am worried about the situation as it concerns data (For long time, data will be backdated).
Thanks.