It happens, it is probably a spawning spot, I have a huge one on my Gourmet farm. If you have already cleared your cache, not much you can do about it unfortunately.
There is a spot on your farm which is a spawning point for a lot of things - items from the barn, visitors for various buildables, etc. it doesn't like to have things put in it.
I would just tell them you had 400 of them ! LUCKY YOU !!!
You need to get a regular order complete to make your 15th in that case. The shared orders don't count toward your personal 15.
You will need to contact support and give them names and their level.
Now whether they can remove ones on the ask list or such not sure if can or not.
I have a ton of people on my ask area that were not friends with but played other Z games with and more and I just work around them.
But on your neighbor bar all can do is hide them. But if ones on your neighbor bar want removed then as said contact support at link below give the name of person and level person is at.
You do not do the tasks that you give to Marie and Barbara - they complete them for you - you just do the ones in the middle.
You can only do so many orders there is a limit of how many orders you can do but think you can still help in a way
Its an ongoing problem from the past several weeks - if you know where you left off on the quests - you can google the guides and continue on - the icons will come back if you complete a quest section but they do come and go so you have to keep track on your own - or you can just not do them or wait to see if they come back on their own at some point.
Discarding the order means removing it before it is submitted - which means you haven't completed it - so it is not counted - it's essentially thrown in the trash.