WHEN I MODIFY A BLOCK IN A COPY OF A DRAWING, HOW CAN I MAKE SURE THAT THE BLOCK IN THE ORIGINAL DRAWING WILL BE UPDATED AS PER THE MODIFIED BLOCK ?
Here’s one way
BLOCKs do not work like that (changes you make in your open dwg file somehow update the block in the source file): looks like you are ready to move to using XREFs if this is a dire project need.
You can recopy back to the source as explained above as a workaround if fixing it at the source first is not an option.
A simpler fix: RENAME the block you no longer want to something else (like MYBLOCK-OLDNAME), then just INSERT the new look old name block into that file.
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