Sure thing. Sorry for my

ty report. I was nervous and sleepy, it was a late night. So the problem is as you can see on the screenshot if there is only two rows of lead glass(or ANY blocks, that merge with lead glass) - everything's fine, but when I add the third row - it merges with painted stucko and becomes a 4 row chunk. Stucko+3 glass. How this works - if there is more than two (like 4 as here) - every row of glass makes the background wall transparent(I literally just added a row of glass blocks on that screenshot) except for the rows on the edge of a chunk(in this particular example it doesn't make lowest wall transparent and it counts stucko as a top row, so makes second and third row a see through window). Vanilla glass works fine. The problem is only in this lead glass.
Ok, so If I am understanding correctly, our problem is that Lead Glass BLOCKS cause OPAQUE WALLS behind them to become transparent, and the Lead Glass is see-through? And this ONLY HAPPENS when you have enough of it? And this DOESN'T happen with Glass BLOCKS?
Am I understanding correctly? If so: That is likely a bug. This behavior you are seeing I believe is the OLD behavior for glass blocks in 1.2, and chances are, Chad just copied it from 1.2 to 1.3. When glass blocks were changed to fix this bug, Chad did not update his Lead Glass to follow suit. But I may be wrong.
You will need to wait until Chad comes back before you'll get a fix, however, as he is """Missing""" as of this writing.
If I am NOT understanding correctly, please write your report again, in numbered steps with 1 image per step, with photo-shopped images of the expected behavior vs. the observed behavior. I apologize in advance for my denseness. Please also do not Paint any blocks, actuate any blocks, or slope any blocks. Use ONLY Lead glass, glass, wood, and wood wall. Crop out all extraneous detail.
Your bug report is important, please bear with me.