What does "mennä puihin" mean?

I had a lovely, hot and sunny month of July and am back! This is Part 2 of my answer to Boglárka. Part one lives here. 

Boglárka writes: 

I haven't really found a good translation for mennä puihin, could you help me out with that? 

The literal translation for mennä puihin would be "to go into the trees", and it means more or less to fail completely or to go very wrong: 

Projekti meni puihin. 
'The project failed.'

A quick googling revealed an interesting second meaning that I don't personally remember ever hearing before, but that my spouse Janne says is the primary meaning for him: 

Menin ihan puihin hänet nähdessäni
 'I froze completely when I saw him'

​In this context, mennä puihin means being unable to speak or do anything in an important situation, like meeting someone you admire for the first time. Basically a deer in headlights moment. So my suggestions for translating mennä puihin would be to fail, to go wrong or to have a deer in headlights moment, depending on context.

Mennä puihin seems to me to be closely related to another tree themed expression of failing, mennä metsään "to go into the forest":

 Mun arvaus meni ihan metsään.
Literally: My guess went completely into the forest. 
'My guess was totally wrong.'​