File Size explosion with design table

I have an assembly with a design table that drives it. The assembly only has about 10 parts but there is a fair bit of logic in the design table. When working on th file yesterday the file size exploded from about 900 kb to 150 Mb (SW 2012 SP5.0).

I think the problem was that at one point when working on the design table i mistakenly copied and pasted a cell to a whole column. I deleted the column but the spreadsheet became very slow to use. My understanding of Excel is that it only stores the used cells so this type of error (even formatting empty cells) can increase the spreadsheet size, which i imagine will increase the SW assembly file size.

To try and fix the problem i have:

  1. deleted all rows below my data in the design table.
  2. copied my data out of the design table, deleted the design table, saved etc, file is still large (even without a design table).
  3. deleted and created new design table.
  4. various combinations of 'save as' and 'pack and go'.

I am at the point of restoring from a backup. Does anyone have any ideas how to fix the file so I don't lose hours of work?

thanks.

SolidworksAssemblies