HDRIBackdrop blurry in reflexions

hey guys, noob question here , i’m trying to get sharp reflexions on windows using an HDRIbackdrop.
My Backdrop is clean in the reflexions but as soon as I rotate it, the reflexion becomes blurry, however the other objects reflexion is clean. I only get sharp reflexion for around 0°, 90°,270° angles. Do you have any advice ?

below are the settings of my postprocess volume
the 2 window images , the sharp reflexion is with the HRDIBackdrop at 0°,0°,0°
the blurry one is at 0°,0°,6°

the glass shader is the one from the starter content



OK I’m stupid, in fact I just had to go yo the skylight component of the HDRIbackdrop and up the cubemap resolution