Ants are annoying and do often seem to appear randomly, there could be a few reasons for ants appearing.
1. You base has blocked the pathing (direction of travel) of the ants and they get stuck.
2. You mentioned food in chests, so having food in chests that are on the ground will attract ants, I had this issue in my first base, move them higher up onto a shelf should limit the quantity of ants appearing
3. make sure you are not putting any ant eggs in chests as they will hatch into ants eventually and cause problems.
4. You could either move the area of you base away from the can to create a path or extend you base to have the can inside your base.
5. You can use some ant totems near the area sometimes this help to keep them away.
If none of these work and you think it maybe a genuine bug you could contact obsidian support and tell them about it.
hope this helps.