Thanks for your answers!

> And maybe in your planar case it's more handy to extrude a surface first drilled by a grid...
Indeed, in case when solid is drilled through this is better approach, but i actually want to randomize drill depth
and in this case i need to boolean...

Still don't get it why rebuilded curves and solids extruded from them causing these problems.
I created curves from scratch and everything seems to work fine...