I have been using ASIAIR with two different RST-135 (I keep one mount as a spare, and for performing indoor experiments) and have not seen the problem that you are witnessing. I use three different iPad pros and an ancient iPod touch which can only get its location through the home network, and they all work.
Be sure to only connect the ASIAIR to the mount's USB port, keep the handcontroller completely disconnected when you power up the mount. Don't even take it outdoors until you have the location problem diagnosed.
If the problem persists, perhaps the ASIAIR app preferences has remembered some old bad coordinates. The only way I know of getting rid of it is to expunge ASIAIR app completely from the iPad; reboot the iPad, and download a fresh copy of the app from the App Store.
Also, when you first launch ASIAIR, you will see a setup page. See if you can the wrong coordinates are also there, and if so, manually change it.
ASIAIR first implemented RST-135 protocols in v1.2, but it was incomplete. They added slew and pulse guiding in v1.3, but the app would crash if you try to do anything to the RainbowAstro mount. At that point, they asked for a loaner RST-150h from Korea (which as far as I know, is still in Suzhou). The RST-135 became fully functional from v1.4 onwards, and we are at v1.7 now.