Posted by Gary S on Mar 29, 2021; 3:13pm
URL: https://forum.librecad.org/Librecad-keeps-adding-blocks-to-block-list-tp5715315p5720480.html

I can't say why there are so many duplicates either, but by turning the blocks off ("Hide all blocks" in the Block List widget) and then turning them on one by one you can begin to see which ones are being used.  It appears that only "0.5-tab", "1-tab" and "3-tab" are being used in the drawing (shop-south_roofing-only_2021-03-28.dxf).  All the others are legitimate blocks with associate entities and increases the files size, but it appears they can be safely deleted.  

Copying & pasting to a new drawing, whether selecting all of them individually or via a select window copies all blocks to the new drawing.

Selecting one of each and then copying & pasting will result in a single block of each.  Pasting a second time will add a subsequent set of blocks.  If you just paste a single block of each, they can then be inserted from the Block List without creating duplicates in the list.  But, that of course means you would almost be starting over...

So, removing all the extra blocks reduced the file from 1.3 MB to 69 kB:
shop-south_roofing-only_2021-03-29.dxf