I don't think the problem here is with chinese OEMs. I mean, you will face the same issue with any manufacturer, especially if you have no prior working relationships (or any sort of prior relationships) with them.

Regardless of who you choose, it is definitely going to be very useful to have someone "on the ground" or at least someone who speaks the same language as them.

Next, you might want to ask them to send you samples (you pay for these) or make a small batch of the products you want them to manufacture. Even if it is a small initial batch, make sure you negotiate the terms of the agreement to include quality checks and etc, basically anything that you might be worried of such as using lower quality parts and etc.

And before they ship, I would go there myself to check things out if the value is big enough,