Pottinger Mex 5 won't always harvest corn

[seacorb]

When using the Pottinger Mex 5 I have to wait up to 3 days in game of "ready to harvest status" to guarantee I will be able to harvest the whole field. If I try as soon as its ready to harvest, huge swaths of corn are not harvestable by either my helper or manually. I have to wait 2 full in game days to be able to harvest and even then some small portions are not ready. Is this a bug working as intended?