Shift between 1sec SRTM and Radiometric terrain corrected DEM


I had to made radiometric terrain correction on s1 SLC image, and in the last part i choosed DEM as output. After, when i compared it with 1sec SRTM, i saw that theres a shift between them (about 20-30m), and made an elevation difference map.
I don’t know if it matters, but before that, i saw in an earlier exported (corrected) DEM, that theres a 40m elevation difference compared to true elevations, so I used the ‘snap.useDEMGravitationalModel = false’ command, and it worked.

Tried to turn it back, and generate a new DEM, but the shift still exists

What causes this shift?