add information about the re-download of files

reanalyses/atmosphere/era5/README.md

 
-# Known issues in the raw data
+# Documentation
+
+Under https://confluence.ecmwf.int/display/CKB/ERA5, one can find documentation about the
+reanalysis, known issues and details about problems that have been corrected in the dataset.
+
+## Known issues
 
 - https://confluence.ecmwf.int/display/CKB/ERA5%3A+large+10m+winds
+
+### Resolved problems
+
+- https://confluence.ecmwf.int/display/CKB/ERA5T+issue+in+snow+depth: files re-downloaded on
+2025-05-08
+- https://confluence.ecmwf.int/display/CKB/ERA5T+issue+in+snow+depth+-+July-November+2024: files
+re-downloaded on 2025-05-08
+- https://forum.ecmwf.int/t/era5-data-from-1st-january-2025-was-degraded-and-is-being-corrected/10689:
+files re-downloaded in early 2025 after the correction was made