This is the 6160th most frequent French word.
faillenet
It seems "faillenet" is not a French word. Were you referencing "faillir" or another term?
Here, 'faillent' is used as the subjunctive form of the verb 'faillir', meaning 'to fail' or 'to falter', applied to a plural subject 'les systèmes de sécurité'.
Si les systèmes de sécurité faillent, cela peut causer des accidents graves.
If the security systems fail, it can cause serious accidents.
In this sentence, 'failli' is employed as the auxiliary verb in a past tense construction, indicating an action that was close to occurring ('almost').
Il a failli trébucher sur un caillou.
He almost tripped over a pebble.
'Faillit' here functions as the third-person singular present imperfect indicative of 'faillir', expressing habitual action of failing to meet promises.