My SKREEM unit has just started acting up and I've been combing everywhere the past couple days to find out the best possible solution. It's been suggested that certain companies can repair/clone SKREEM modules, but nobody has actually reported back and confirmed success in doing so. ModuleGods has been suggested elsewhere in the forum as a provider of a possible fix, and I'll be trying to get in touch with them tomorrow to see what they claim they can do.

In the meantime, I did find some interesting material that might assist in understanding how the modules may be interfaced with and reprogrammed.
See here: https://www.arlabs.com/locksmith_doc.html
The page contains documentation for many different immobilizer and ECU units, including ours ( Mercedes 170 820 18 26 ). See here: Mercedes_170_820_18_26.zip

Although I don't have the hardware or expertise to perform the demonstrated diagnostics, I suspect some of our members here might. Hopefully this provides some utility.