I just reopened my game again today and the collection is still there. I did have a couple sims move out before the collection reset. I used to be able to move them out without having to worry about the collections resetting.
My level 10 gardener already had everything in her inventory and fruits and veggies in the fridge, but the collections is the one that was resetting. Fortunately their garden is always ready to harvest so if it keeps resetting then I can just collect them again.
The only way that I can seem to finish the collection is by getting the cow plant berry from debug mode and setting it in her inventory. I can't figure out how to get the cow plant berry any other way. I've done the kill a sim by cow plant thing in another game save, but I only get the essence of that sim from it not the berry.
