The Aprilia rider came into Sunday’s 25-lap grand prix in Portugal as one of the favourites for the victory, having won the sprint on Saturday.
Vinales was a factor in the victory battle from the off, breaking away from the rest of the field between eventual winner Jorge Martin and Enea Bastianini behind him in third.
But from the early stages, Vinales started to suffer from a gear selection issue between fifth and sixth gear.
As he accelerated onto the pit straight to start the last lap, his Aprilia went into neutral as he tried to change to sixth gear, which led to his sudden slowing down while running in second.
Vinales then says the bike suddenly engaging second gear when he touched the accelerator after running off at Turn 1 led to him crashing out.
“After the uphill on the finish line, I tried to put sixth but it didn’t go in,” he explained when asked what happened when he slowed onto the last lap.
“So, the bike goes into neutral and I hit the limiter. I just put out the leg to [warn] Bastianini to understand that I had some problems [and] to go away.
“I tried to put sixth, it didn’t go in, I go back to second and when I touched the gas it went in immediately and I high-sided.”
The issue largely affected him on the main straight, with Vinales reckoning he lost 0.2s every lap because of it.
While he implored his Aprilia team to improve reliability – having battled various bike issues late last season – Vinales says he has to be happy with the speed he showed all weekend in Portugal.
“I think we must be positive,” the Spaniard said.
“I would say it’s not a disappointment, but I will say it as maybe a call of attention, trying to improve in some ways a little bit the reliability.
“I really encourage all of the Aprilia technicians to improve on that area, especially if you want to fight for victories.
“After that I think it’s been amazing how when I get the correct balance I can go really fast on this bike.
“Despite the problems I had from lap six, from fifth to sixth gear sometimes it didn’t go in.
“So, I was keeping the rpms for so long and I was losing a lot on top speed. I was losing some tenths, but despite that I was able to do 1m38s and that was amazing.”
Vinales added that, even with the gearbox issue, he still believed he could fight with Pramac’s Martin for the win in the last laps.
“I thought all the race that I could fight for the victory, just the problem was every time the gearbox got worse and worse,” he noted.
“So, every time I was losing more and more on the main straight.
“I think I was losing 0.2s on the main straight and then I would recover all the gap again.
“Even with this problem I was in 1m38.8s. It was unbelievable because it could be 1m38.6s. I’m really happy."
