Near the halfway mark, Bottas radioed in to inform his team of the seatbelt problem, subsequently pitting in order for a mechanic to tend to the issue. Williams' Rob Smedley now wants to know why the malfunction occured.
"His seatbelt came undone, he told us on whatever lap it was, so we pitted immediately and did them up again in the pits," explained the engineer.
"We need to understand why they have come undone, because it is really quite a worry in itself that seatbelts come undone while they are driving at these sort of speeds."
Smedley was reminded that Bottas was confronted with the same issue in the 2014 Brazilian GP, but he didn't believe there was any common cause between the two mishaps.
"I don't think it is a similar issue, but it was a seatbelt issue. As usual we just have to go away and do the correct analysis and due diligence.
"But the main thing is that we fix it for Malaysia and see what it was. We have done all the season without the seatbelts coming undone in the practice or race or anything like that, so it is a bit of a worry that it suddenly just happened."
Bottas retired on lap 35, ultimately with mechanical damage probably sustained at the start of the race when his Williams was hit by a McLaren, enduring a puncture which forced the Finn into the pits on Lap 2.
"Valtteri's race was almost done on that first lap when he got a puncture and dropped to the back," said Smedley.
"We suspected he had mechanical damage after his last pitstop, so the best thing to do was retire the car."