A year ago I updated from Mint 18.2 to Mint 18.3 using the quick method available in Synaptic Package Manager. A few days ago I updated to Mint 19.1 by installing from a usb stick. In each case, before upgrading, I saved my software selection using the Backup tool. I have separate partitions for root and Home so it is easy to upgrade.

The latest software selection only contained the applications I had installed in the last year, for some strange reason, so it was my intention to restore both software selections to get back to my previous configuration. Restoring the most recent software selection was successful but restoring the old selection was not. I can sometimes get to the point where I have navigated to the appropriate software selection file, all the applications are listed and ticked and then it crashes, either by itself or when I click Forward. The Backup tool looks quite different, so changes have been made to it.

It looks like a bug to me, but can anyone suggest a workaround so that I can restore my applications?

Problem solved. There is a limit on the size of the file
https://github.com/linuxmint/mintbackup/issues/59

The file was 44.8K. I have previously successfully restored a file that was 38.3K so it looks like the limit is about 40K. I split it into two files and it worked perfectly.