Hi SBC. Not sure what you mean by "Could this be due to an update"? An update by who and/or how and when?
You don't mention your vehicle being back at the Dealership in the 3 weeks after you replaced the APIM, so unless you personally applied a software update or your vehicle was back at the Dealer and they did, there is no way any updates could have been applied.
My blind Internet guess? Since unplugging, replacing and plugging in a new APIM seemed to correct it for a while: Possibly a loose/improper connection (corrosion)? Or an loose/bad ground? Or an intermittent short in the wiring?
Did you hold onto the old APIM? If yes, I would try swapping them again to see if jiggling the wires gets it working again. If it works with the old APIM, then it would seem to be a wiring or other type of issue. If it does not, switch back to the new APIM and see what happens. Since it in only a 15 minute job, the time spent would seem to be more than worth it.
If none of that helps, you may want to get a few estimates from independent shops that specialize in electronics/electrical work.
Perhaps another member has more insight into a cause and will jump in to help.
Let us know how you make out and good luck.