I thought I fixed that
Will check again

I unsubbed and re subbed to the mod. There seemed to be some update happening through steam. Unfortunately it seems the zombies are still disappearing.

I can spawn them now in debug with the mod activated (one month and 21 days in), but when I quit the game and load back in they disappear. Tested on some organically found zombies and they disappear too.

Do I need to start a new game for them to remain persistent? Does the "week one and beyond" mod fix this? Otherwise I will have to disable the mod, which is a shame because I would still like to have the chance of encountering npcs now and then.

Could you please have another look at it, and evaluate the long term consequences of the mod? Its way too easy to get generators when "hostile defenders" move into my shed or barn and leave a fully functioning generator behind. I have 3 extra generators now.

Have you tried with just with this mod and bandits? I update my code but other mods overwrite it sometimes and don't update as frequently.