Alonso and team-mate Lance Stroll had been struggling with the DRS overtaking device all weekend on their new low-drag wing for Baku's long straights.
The problem came up in Friday practice and continued all the way through both qualifying sessions this weekend, and while Alonso reported no problems during Saturday's 17-lap sprint race he wasn't totally convinced the issues is fully resolved for today's grand prix.
"That's the topic this weekend in our team, but it did work. I think in the race I pressed two times and it did open, so I hope everything is fixed," Alonso said.
"One third time I wasn't looking at the mirror, so I'm not sure but I'm sure the team is analysing all the data available and if we have some tweaks to do we have another chance before tomorrow's race.
He added: "I think we cannot be 100% sure [it will work in the race]. We've been through problems every session, so I don't think that the system is still bulletproof into tomorrow's race, but it's the way it is.
"Even with a DRS it seems very difficult to overtake when you're following cars, so maybe it's not the key factor tomorrow. Even if it doesn't work."
The DRS gremlin had cost Alonso and Stroll lap time and bumped them down to sixth and ninth respectively on the grand prix starting grid.
But even without it, Alonso admitted Aston Martin's pace hasn't been as impressive as in the opening three rounds, having lost out to both Ferraris and at least one Mercedes in all competitive sessions this weekend.
"I think that the weekend, in general, has been a little bit worse than the previous three races," the two-time F1 world champion explained.
"We are underperforming a little bit, [Saturday's sprint shootout] being the best example. P8 and P9 is not good enough, so we were a little bit concerned into the race.
"But in the race, I think I have to say that I'm more optimistic now after the sprint race that the car will be fast.
"I was fast in the sprint race, I was at the pace of the Ferrari and the Mercedes.
"I start P6 instead of P8, so we still have a chance to finish top five, which will be ideal. If we can finish sixth on Saturday, top five on Sunday on a difficult weekend that will be very good news."
Additional reporting Oleg Karpov
