Can you perhaps send us an application demonstrating this issue? We are unable to reproduce this and unaware of any issues with the TMSFMXWebGMaps.
Apparentely "argument out of range" appears when I add the first Marker on the Map, or when I try to obtain address with the ReverseGeocoder procedure. TTMSFMXWebGMapsReverseGeocoding is on version 188.8.131.52?
Did you enter a correct address, does the content that you add to the marker contain special characters? Unfortunately without more information we are unable to determine what might go wrong in your application, or if it is an issue in our component. We have tested our demo here and are not able to detect any issues.