Many importers, both new and experienced, can often be fooled by the English abilities of their supplier along with all of their staff. Requests for prices, shipping information, product information etc. are responded to with near perfect English (minus the inevitable difficulties in differentiating between plural and singular!). It's an easy conclusion to make that your Supplier and all of their staff have perfect English comprehension.
This of course is a false assumption to make. Even if your supplier truly has perfect English (which is highly unlikely if evidenced by nothing more than my wife's English after living in Canada for over half her life!) few if any of their staff members will. So when your contact sends instructions to their factory things will inevitably get lost in translation.
I had this problem recently with a supplier. We started importing a new product from a long time supplier and I asked them to package it in a white box (rather than brown box) with our sticker on the front. The first shipment used a brown box. I reminded them again on the second shipment and they sent a brown box with a small sticker on it (think the size of a postage stamp!). Finally I opened Photoshop and made a rough 5 minute drawing of how the box should appear (which essentially was a photo I found of a white box on Google with our logo super imposed on the box). The next shipment it was perfect.
When you are making product and/or packaging suggestions always use a picture when you can in lieu of words. Photos can be understood by anyone, regardless of language or literacy. So if you are importing hiking pants and you want to include a pocket half way down the leg, take a picture of the pants, open the picture in Photoshop or MS Paint (or other editor), draw a sloppy picture of where you want the pocket to appear on the photo and send it to them. You'll see drastic improvements in receiving your products exactly how you want.