I compared the Rome and Medieval descr_engines.txt and found the Medieval file lacks the engine_model lines found in the Rome file.
Code:
engine_model data/models_engine/mining_tunnel_high.CAS, 20.0
engine_model data/models_engine/mining_tunnel_med.CAS, 40.0
engine_model data/models_engine/mining_tunnel_low.CAS, 80.0
engine_model data/models_engine/mining_tunnel_lowest.CAS, max
Putting these lines in place as well as the corrosponding .CAS files they reference, I gave it a test run. No sap points were available in Custom or Campaign sieges. Then I checked the log and found this.
Code:
Script Error in mods/expanded_americas/data/descr_engines.txt, at line 1773, column 22
Unrecognised engine class sap_point.
The models_engine folder seems to be largely un-used in Med2, siege engines are referenced to the siege_engine folder by the term engine_mesh as opposed to engine_model in Rome.
But with the sap_point showing as an 'unrecognised engine class' in the error log, the problem of models seems largely irrelevant.