Some ok and some not ok? Really interesting. Why not setting a static ip for those clients?

Eslam Saied wrote any update? i have same issue I think you need to set as uutommi said. The OS on router are always old linux and NTFS is too new to them. As you can see at...

You need to a check. There is a button you should active first or you cann't set like this guy http://forum.tp-link.com/showthread.php?77347-TD-W8970-can-t-enter-Bandwidth-control

StanicEnemy wrote im having the same issue can anyone help? Have you upgraded the firmware to the last one?

TD-W9980 is the only one which do not support G.vector . I think it may be related to your issue? Greece ISP seems have a update on their DSL. Try a TD-W9970 (even cheaper? i guess) maybe good

Qos is a trash on TP-Link. You can not believe it . Actually Qos is a complex function and what TPlink has is just a simple edition A router can work well good on Qos? A joke of fun.HAHA