9920 or mgm 160

[RC-Monster Mike]

It sounds like the voltage is dropping on the Lipo pack and causing the controller to cut out. I had this issue myself. I actually changed the battery parameter back to nimh/nicad and the problem seems to have disappeared(I wish I had done this a couple days ago, as I had the cut out issue at the RC-Madness race, which cost me some time!). The constant beeping would suggest that you may have the battery setup on 3s Lipo or something besides nicad/nimh or 2s lipo. If theis parameter is set to anything besides nicad/nimh, the controller will beep the error code unless the proper battery is plugged in. I struggled with this myself, but I think I have the quirks pretty much figured out.
The 160 amp controller is a sweet thing, by the way. Once the bugs/uirks are worked/figured out!