Well… looks like I’m an idiot. The wireless access point that had been moved nearby during the renovations was indeed generating a significant amount of activity on the IR receiver even when nothing was being pressed on remotes. I had no idea that 802.11n/ac protocols would interfere with IR activity, so it didn’t even occur to me to worry about placing an access point nearby. I just needed a port to plug the WAP into temporarily while it was away from its normal space in the house, and the switch by my media center was the most convenient.
I ran an extra-long cable from the switch to move the WAP to another part of the room, and now I only see very occasional pulse and space lines when nothing is being pressed, not a constant scroll of activity. Testing the remote with standard lirc shows it working just fine again.
I’ll probably still rotate over to using the ir-keytable mapping, since it appears more functional/robust overall, but the basic issue was clearly just the wi-fi proximity. It was total dumb luck that I pushed the May update on the same day I moved the WAP, since I often run pending updates on my devices on days where I’m working on other things around the house and don’t expect to be using them.
I’m editing the thread title now and linking the top post to this one so no one else gets confused.