Ideas
The exact same thing happens to me as was stated by others here. It wont save a custom preset. when i initially save the preset, its there in the drop down but when i leave the lot and come back, the preset is gone. When i make changes to a default preset, the changes are gone, in fact the preset is not selected when i go back into the lot. This is with and without going into the uniform option. I deleted the thumbscache ect, rebooted, still wont keep the preset with the lot in build.
HOWEVER. I gave up trying to edit it and just had a sim do a getaway and i was able to do all the customization through the getaway plans even if you need to change how many for each role or add roles. Side note, you can't add people to the getaway who are not in world.
EDIT: If you are in a getaway and have to save and close, the getaway will be gone. I dont remember this happening with the kids camps that i did but the romantic competition i was just working on, broke. When started the game again, the progress was there as far as relationships ect, but there was no schedule/rules or anything. All the getaway people were there as if it was just a vacation. Since the modify custom venue function doesn't work, you can't re-apply the getaway rules and schedule. The only option really is to start a new getaway and I guess only play when you know you can finish it in one sitting.