The field within the attribute definition within block editor is not functional. The fact that it is functional in another file, just means that the block definition and more specifically the attribute definition within it has been changed and broken. This fact is demonstrated by ATTSYNC wiping out the definition AND can also be confirmed by viewing the block in a test window within block editor. My guess is that the fields are referencing the construction lines and the link is broken for the inserted block as construction lines are not shown, but that is just a guess.
Here's something that I believe will work more solidly and actually simplify the block a bit. Instead of using an object field that references a construction line, use a BlockPlaceholder field referencing one of your linear parameters. I have found that oftentimes when attempting to change a field's definition, it does not work. It seems to always work to open the attribute editing dialog, delete the field from the default value, exit the attribute dialog, add the new field definition. Give that a try and then report back how it works out.
As an aside, if you are not rotating the block, then it would likely be more appropriate to use an XY parameter instead of the 4 linear parameters. The field would then need to reference the independent X or Y value of the XY parameter.
