@3dsurfr thanks again. I measured my base plate(heat Bed) on cold and it has a curve of >=0.4mm less than 0.5mm i am pretty sure a few months back was not like that. I have been printing mainly at 110C ( abs/asa ) . Only in one direction is curved the other direction looked ok or is less than 0.1mm. And on hot is bigger still to do do accurate measurement so do not think this was warping 
Other direction less than 0.1mm if any :
I will request from Bambu to change it to see what will happen , but if there is design issue will bend( curve) again
EDIT: after heating the bend is > 0.6mm < 0.7mm