KSP Interstellar Extended Thermal Jet Issues

[Nazamroth]

Dear Kerbonauts

I have finished the tech tree with science spamming and now I wanted to make use of it. Using thermal turbojets seemed like a decent option for an SSTO meant to go to and from anywhere since it can use the atmosphere with no fuel consumption for good-ish thrust, and provde extra boost in space with different fuels.

However, it drives me insane. When I attach it to some random node, it works just fine. But when I put it anywhere useful, like a bicoupler in the back, it totally breaks. It only allows me to select from about 5 fuels, when I launch it it goes down to just hydrogen, and then it accepts neither liquid, nor gas hydogen when I try to at least test that.

If I take the working jet, set it to atmospheric, then place it in the back, it will switch to hydrogen as soon as i launch, and then stay like that when i revert to the SPH. 

Has anyone encountered something similar or at least knows what may be causing the issue? 

Thanks in advance.

 

Ps.: A fine spaceplane prototype was turned into a mess of a test bed due to this. Do it for her.