Why does Simutrans Standard maps not work on Simutrans Experimental? :(
I suspect that some differences in the saved game format have arisen between the two that have not been resolved fully (or there are some changes to Standard that affect the saved game format that have yet to be incorporated into Experimental).
Fixing this would probably take many months of work, and, given how different that Experimental has become from Standard, the utility of loading a Standard game in Experimental is limited. For these reasons, I am afraid that this is not something that I am able to prioritise.
Thank you for pointing out the issue, however.