Weird lightmap problem

Hi, i’ve had this problem for a few days now. I have a mesh with 1024 lightmap (see screenshots) and after i build lighting there are places on the mesh where there is no lightmap, i don’t know why. Do you have any idea why is this happening ?
Thank you

This is lightmap bleeding issue which I experienced back in UE 3 days.

#1 Try to increase lightmap size to 2k or 4k.
#2 Increase spaces between faces in lightmap UV.

Let me know the results.