When I use the geocoding tool to plot cities/states in the U.S. it plots only one point. However, the attribute table shows that all the points have been plotted. Furthermore, the one point is not accurately located on the OpenStreetMap (the point is in TX according to the attribute table when I select the feature, but it is visually located on Kansas). They are not plotted elsewhere when I zoom to layer (i.e. they are on the same CRS).
The file not in utf-8 but it is in utf-16 as it is seen in the error message. Unicode representation point to utf-16 encoding
Encoding Representation (hexadecimal) UTF-8[a] EF BB BF UTF-16 (BE) FE FF UTF-32 (BE) 00 00 FE FF
as shown here, hence the tool is not recognizing the address
which QGIS tool were you using to do the geocoding and which QGIS version? I highly recommend using the long term release version of QGIS (currently 2.18) if you aren't already.
I haven't used a geocoding tool in GIS before and since I don't know which tool you used I can only give some general advice. I hope it will still be of use to you:
I did a little research online and found this website which also comes with a video tutorial. It uses the MMQGIS plugin (you can find this plugin under Plugins in QGIS and install it). I hope this tool and website will help you achieve your goal or if you have already used this tool, that the website can help you find the error.
Here is the link: https://www.gislounge.com/how-to-geocode-addresses-using-qgis/