Troubles with TileSet Editor

I created a set of elements and tried to mark the block I needed, but when I click on one block, in the editor chooses completely another block.
For example, I click on block that marks cross
When I zoom image to state Zoom x5 then position of cursor and choosed block are nearly matches (if I click not on center of block the mark will be on another block)

I choose UE 4.19 and UE 4.20, but result is same