Anyone modifying existing block attributes has run into the mysteries of how to update the existing blocks on the drawing. Reinserting the block doesn't update the attributes. I should be using Swap/Update block. However when testing I tend to keep the changes inside the test drawing using embedded blocks. Doing this means the existing occurrences of this updated block must have their attributes synchronized.
The only problem I have with this method of updating existing blocks is having all attributes return to the blocks default layer. Today I learned when using the Swap/Update block all attributes are placed back on the proper Electrical layer. This is a great little discovery. Now I can continue editing the block within the drawing until I’m happy with it, then WBLOCK it back out to the library. Following that up with an Swap/Update puts existing blocks back in order.