Bobcat S220 weird electrical issue

2006 Bobcat S220 about 2k hours. I went to start the machine and as soon as I tun the key all of the panel lights blink in unison with an alarm every second or so. No engine crank. When I turn the key to the off position the alarm and lights continue. No codes are displayed. Only way to get it to stop is to disconnect the ground side of the battery (prbly positive would work, but easier to get to ground) or pull the fuse to the computer. I can hook ground back up with no alarm but as soon as I turn the key, same thing happens again. Fuses are all good. I pulled the battery clamps, cleaned and installed. Pulled all the grounds on the back of the machine, cleaned and installed. Pulled 100 amp fuse, cleaned and installed. Still happening. Battery at 12.83v, load tester said it was fine. The primary ground wires all have continuity to ground. No amp draw on the battery, so I dont think its a short but I could be wrong. I was testing the wiring harness back to the fuel sending unit a few days ago as the fuel gauge is on the fritz. Cleaned connections and reinstalled then ran it for about 30 min, no issues. Parked it in the garage. Then go out this afternoon to move a down tree, try to start and this happens. Not sure it's related to the troubleshooting I was doing before, pulled side cover and the connector is looking fine to me. Any ideas where to start? I could really use some ideas. I can't find any reference to this issue online or in the service manual. First time I've had anything like this, it's been a solid machine. Thanks in advance, I really appreciate any input.