Line 50, unfortunately leads to subtle software bug (7)

I believe the answer is:

illness

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'bug' is the definition.
(thesaurus)

'line 50 unfortunately leads to subtle software' is the wordplay.
'50' becomes 'l' (Roman numeral).
'unfortunately' indicates anagramming the letters.
'leads to' is a charade indicator (letters next to each other).
'subtle software' becomes 'ss' (this might be a standard abbreviation I've not previously seen).
'line'+'l'='linel'
'linel' is an anagram of 'illne'.
'illne'+'ss'='ILLNESS'

Can you help me to learn more?

(Other definitions for illness that I've seen before include "suffering this" , "Complaint" , "Upset" , "Indisposition, sickness" , "Ailment, disorder" .)

I've seen this clue in The Hindu.

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