The rectangle burn shows after washing and it's BAD

Hello guys. I place an order with every t shirt promo, and the last 10 t shirts or so have a problem. You do seem to have a problem in production. it seems like there's a rectangle gadget that stamps the t shirt in high heat to imprint the design. The problem is, with light colors like whites and greys, it leaves sort of YELLOWISH imprint all over that space. and it leaves the t shirt unwearable. The last 10 t shirts or so do have this problem. even when I tried avoiding it and placed a logo for 3x3 inches space, the t shirt still came burnt with the big rectangular area in the middle. and this time it's detectable even before a wash! It seems like the heat adjustment on that machine you use is set to VERY HIGH and it burns the cloth rather than just imprints the design. I'm very dissatisfied, and as easy as it was to order, from now on, I won't be ordering again.