On iPad Pro 12.9 : why my photos appears blurry until I zoom inside?

Hello all,
I'm a new user of Lightroom on iPad Pro (I use it on my desktop computer from years) and since I started using the mobile version on the iPad anything is constantly annoying me :
Why images in collections, albums (even when stored locally) always first appears blurry like if it was a quite low res preview?
I need to zoom in the picture and then dezoom to see it in the good and sharp quality. It is not a problem of size of the picture or heavyness of the file has I've tested with pictures sized in the native resolution of the iPad (2732px in the largest dimension). Even when the picture is correctly displayed (after I zoom and dezoom), if I swip to another and then get back to this previous picture, it is again displayed in the poor blurry version... it is really annoying.
This appens every time, even with pictures stored locally in the iPad, so it is not a sync problem. It is really strange.
Thank you for your help.
Xavier