Sims not appearing at community lots in college.

I have a strange and annoying problem.

When I send a Young Adult sim to a community lot, or a group of them, the community lot loads and other (ie visiting) sims appear on the lot and walk around as usual but the sims I sent never arrive. I can't seem to notice any pattern to it as it happens in some households but not in others, apart from:

- It seems to have been triggered both times it has happened by telling the sim(s) to "Walk To Lot" rather than use a taxi or car. But if I subsequently tell them to call a taxi, they get into the taxi, the taxi arrives at the community lot and they don't ever get out of it.

- When I reloaded the entire game and went on one of the affected households, and directed a sim to call a taxi, it worked fine and I could then get them to walk to lot or use a car.

- It doesn't happen on dorms, only normal houses on the college campus. I don't have any greek houses.

If I get stuck on the community lot with no sim to send home, the only way to get back is to exit to neighbourhood and load the home lot - but the sim won't return from the community lot and since they are off-world I can't force an error on them. If they went in a taxi, the taxi returns but the sim doesn't appear in it. The taxi is stuck in a loop and doesn't leave. And then if I go to the options menu, save is disabled and clicking on exit to neighbourhood brings up the dialogue about exiting a community lot using the menu, even though I am on a home lot.

The only way I have found to fix this is using the lot debugger to nuke scenario controller and reenable controls, but the sim won't return unless I force errors on all off-world, which takes forever, and generates so many error logs I can't work out which one (if any) I need to post.

I can try taking hacks out but I don't know if that would help as it seems to be intermittent, I can't seem to recreate it when I want to, it only happens when it is least convenient. The only hack I have which I can think of which might interfere with these kind of things is the Community Time Project, which works fine in all other ways.

I only ever make them visit lots on campus.

I have all EPs up to FreeTime except for Bon Voyage, and no Stuff Packs. Any ideas?