Solved

reliability

Did you upgrade the design facility lately? Doing that greatly increases parts needs in those levels, often to the point even maxxed out manufacturing can't produce nearly enough. There's 3 things you can do:

1)Buy parts with tokens

2)Get the App, if you're not already playing on it, and on the page you can buy parts/engines there should be a blue button below saying Free Parts. It gives some parts for watching advertisement videos, up to 10 daily I think, but people often run into issues earlier than that because it seems to be sometimes buggy. According to the number of posts about it in the forum that is.

3)If you don't want to, or can't, do either of above (regularily) you can try to get by long enough by repairing one car and the other next race and so on. Unfortunately you are still very early into the season so it might be necessary to sacrifice one car to keep the other running. Keep in mind that after the last race you get a fully repaired car without the use of parts, so get the most out of this. Reliability can safe you some parts but the effect is very small, unless your Reliability is extremely low. In the long run you'll have to keep manufacturing maxed out and design slighly lower until you hit levels again where manufacturing gets closer again to actual demand and eases your parts situation or until you managed to collect a large enough stockpile to get you by.