Hope, this is the right place to report, but it feels like an issue to me (in fact, somewhat pressing).
I have serveral wiki systems live where I make use of Semantic Forms in conjunction with smw or cargo. I noticed this behaviour on multiple systems so I am inclined to think, it is not a user problem.
On form fields that use autocomplete with mapping (tested with mapping cargo XXX and mapping property respectively), mapping starts to fail as soon as the list exceeds $sfgMaxLocalAutocompleteValues. I recon, that is the point where SF switches from a prepared local list to remote autocompletion. What is breaking user experience is, that I autocomplete over categories that are filled by users. So at a certain point the forms starts to behave differently. Also in one occasion I rely on the use of SemanticTitle, because my page names have numeric IDs - data the user has no way of knowing what it represents. So the user, in turn, has no chance of knowing what to input in the field.
MW 1.25.5 with SMW 2.3.1 (private system)
MW 1.23.13 with Cargo 0.11 (read access to *)
Both tested with SF 3.5, Cargo also with SF 3.6alpha
Is it in fact a problem with the extension or did I do some misconfiguration?