some web pages only accept requests from mobile devices
but --random-agent only suitable for PC or other desktop device
and --mobile can't do that (randomly and automatically)

and........... you can try to inject the header X-Forwarded-For or other similar
because some websites track and record your IP to their SQL server

https://github.com/sqlmapproject/sqlmap/blob/master/tamper/xforwardedfor.py
https://github.com/sqlmapproject/sqlmap/blob/master/tamper/varnish.py
http://airs-sec.com/2017/08/26/sqlmap%E4%B9%8BX-Forwarded-Host%E6%B3%A8%E5%85%A5/