According to ESA, "the root cause was traced to a software timing bug. The function that switches the signal amplifier on and off uses an internal timer, which increments and restarts from zero every 16 months. If the function happens to be using the timer at the exact moment it restarts, the amp remains switched off."
Sounds like an unsigned 32-bit counter that counts every 10 ms and rolls over in 497.1 days (~16 months) and some faulty logic like t1 > t0 + delta?
https://www.esa.int/Enabling_Support/Operations/Juice_team_resolves_anomaly_on_approach_to_Venus
2/n