In recent years I have used this source https://dds.cr.usgs.gov/srtm/version2_1/SRTM3/ to retrieve elevation data from files in .hgt format. The problem is that these data have holes, so I'm looking for a more recent source of SRTM data, which I found here http://srtm.csi.cgiar.org/srtmdata/ with .tiff format files
The holes have been filled, that's good, but the overall quality of the data returned is really worse, and I do not understand why.
I made an example of traces on contour lines using both sources, and here are the results I get: https://www.visugpx.com/yXT5LMErgk
You can compare the graphs for traces on 500-meter contour lines (on a steep terrain), 320 meters (hilly terrain) and 210 meters (flat terrain), and see that for the SRTM v2 .hgt source I have a margin an error of a few meters, while for the source SRTM VR .tiff there is up to 30 meters difference.
Is this problem known? Are there other sources you would recommend?