Quick update. The current experiment is

1. Separating out the roots more when transferring from the seedling container and leaving a bit of soil on to help retain moisture (I still think that root development during the seedling stage in the misting chamber will improve things, as finer roots will develop. That remains to be seen. I'm growing some plants from seeds to experiment with).
2. Closing up mist escape routes (see the ugly masking tape in the photo below) to retain more mist in the chamber as the main problem at the moment seems to be loss of water in the plant. The chamber is still connected to the outside air through the fan port. I just had an idea about this!

Photo evidence: