Sauber introduced more advanced pitstop equipment for this year, but from the first race in Bahrain, it has encountered cross-threading issues on the wheel nuts, which led to disastrous pitstops over the first few races.
The Swiss team made some modifications and changed procedures to mitigate its hardware issues since Bahrain which has generally worked, but Sauber's pitstops are still generally slower than its midfield rivals.
Those problems have already proved immensely costly in the tightest midfield battle in years, with Sauber's Bottas and Zhou Guanyu still left without points while RB and Haas have already managed to get on the board.
Speaking ahead of this weekend's Chinese Grand Prix, Bottas said the team was introducing further modifications for the Shanghai race, but a permanent fix remained unavailable.
"It's a difficult situation and we shouldn't be in this situation, but we are and now we need to get it sorted," Bottas said.
"There are further modifications for this weekend, but it's not 100% fixed, so we know it's not yet our strength for sure. If anything, it can be our weakness, but we're trying. Let's hope that things go smoothly now."
When asked when he expected a permanent solution to arrive, he clarified: "By Imola."
Sauber's weakness was on full display in the Japanese Grand Prix when Bottas pitted together with a gaggle of midfield cars on lap 23.
Bottas came in from 11th place, behind Haas' Kevin Magnussen but ahead of a train including Logan Sargeant, Yuki Tsunoda and Lance Stroll.
Bottas entered the pits in second position from the group but came out in fourth behind Tsunoda and Stroll, and his slower stop also meant he was undercut by the struggling Alpine of Esteban Ocon.
Tsunoda, who came out first, went on to claim a point for RB on his home turf, which Bottas felt could have been him as his Sauber had similar pace.
"We've been improving race by race, and that's because we've been bringing bits," the Finn explained.
"In the last two events we've been, in terms of pace, very similar to RB and Tsunoda.
"The issues we've been having, especially with the pit stops, that's been masking quite a bit what the actual race results should have been.
"For example, in Japan before the first stops, I was ahead of Tsunoda and with similar pace, and he finished in 10th. So, I think we haven't really seen the full potential yet.
"We are aware that most likely if we stop at the same time as our competitors, we have a bigger chance of losing the position.
"We'll try to optimise for that, but hopefully that doesn't need to be the case. Hopefully, we are getting that consistency and 100% fix in a couple of races."
