Dryhops,
I dug through some of my post histories and it jogged my memory, you probably already have already realized I did your original Ignition application.
Back when I commented to Laura: AB CompactLogix firmware 21 issue:
I now recall trying v21 firmware during the development stages and had a number of problems with it. I even remember setting up Kewpare to compare the results, and Kepware worked great. This led me to roll-back to v20 for the original system. Given that you’re still on v7.7, change the PLC firmware to v20. This will solve your problem and function like your other PLCs. You can then evaluate your path forward to update Ignition to a newer version, then you could evaluate updating your PLC firmware to somthing newer.