After weeks of troubleshooting, NASA and Boeing still can’t set a return date for the astronauts on Boeing’s Starliner spacecraft, which is facing issues such as helium leaks and thruster failures.

Recent tests have revealed that heat buildup in the thrusters may cause Teflon seals to bulge and restrict propellant flow.

Engineers have replicated the thruster issues on the ground, providing insights into the problems.

Boeing and NASA have decided to forgo manual flying of the spacecraft to avoid extra stress on the thrusters.

While there’s a push to return astronauts Butch Wilmore and Suni Williams home aboard Starliner, officials remain cautious and have contingency plans if necessary, CNN has reported.

The astronauts have been in space since June 6 and could stay up to 90 days.

Written by B.C. Begley