Geoff,
It seems to be a bug in ARCHICAD, I’ll add it to our bug database. While testing it, I found a “dirty hack” as workaroud: if I add the same amount of hotspots in the same order to both the mirrored and normal sides, then all the hotspots starts to work normally. To reach this, I added the len and thk values as params, and created editable hotspots to the block side of your objects, and commented out all non-editable hotspots from your script. I also commented the text type editing hotspot – so I only had 2 editable hotspots on both sides. I hope it helps a bit.
Gergely Fehér
Team Leader, Library Team
GRAPHISOFT SE