Why not taking off?

[martincmartin]

According to both Kerbal Engineer Redux and AeroGUI (and all the other times I've played KSP), the following rocket should lift off the pad.  In fact, it should have a TWR of just under 2.0.  However, a few seconds into flight, it still hasn't lifted off.  What's going on??

Also, it tilts to the left, despite being symmetric and having fins.

Something is horribly wrong.

The rocket is very simple: two thumpers and a Stayputnik, with 4 fins on each thumper.

Update: exiting KSP and restarting it has fixed the problem.  Still a mystery as to why it was happening, or how to notice something like that is happening again, with other rockets.

Imgur albu

Edited March 19, 2016 by martincmartin

[Kerbart]

The question is... which of those two thumpers is being ignited first?

[martincmartin]

4 minutes ago, Kerbart said:

The question is... which of those two thumpers is being ignited first?

  The bottom one.  If it was the top one, it would instantly overhead & explode the bottom one. Believe me, I've gotten it wrong many times.