After weeks of troubleshooting, NASA and Boeing officials say they better understand the issues plaguing the Starliner spacecraft, but still aren’t ready to name a return date.
tl;dr
Heat building up inside the thrusters may be causing Teflon seals to bulge, restricting the flow of propellant.
Heat? In my thrusters??
It’s more likely than you think.
Who could have known that heat makes things expand?