Stability improvements

[fikovnik]

It would be great to somehow improve the robustness of the sxpdb so ti does not crash R that often. One thing could be to try to run it with some sanitizer to check possibly invalid memory access.

[programLyrique]

That should be doable: https://cran.r-project.org/doc/manuals/r-release/R-exts.html#Checking-memory-access