Understanding Society User Support

Query from Curtis - Channel 4 want to use this data quite urgently.

A slightly random question - I've been looking at BHPS data on young people's opinions on the likelihood of future events ([W]FUTR[X]), and it doesn't look quite right to me.

For example, between 'LFUTRE' & 'QFUTRE' - 'Likelihood: Long term unemployed' there is an apparently very large shift in the percentage of participants coding '0%', related to a similarly large shift in those coding 'Doesn't apply'.

Wave 12 - "Doesn't apply" - 1%
Wave 17 - "Doesn't apply" - 39%

Wave 12 - "0%" - 40%
Wave 17 - "0%" - 8%

I noticed in the questionnaire the code for 'Doesn't apply' seems to be '0' - I was wondering whether this might have caused some confusion? Or am I seeing problems where there are none?