UKH

It scared me half to death and yet it gets just one star on Rotten Tomatoes!

Rotten Tomatoes is not a good indicator. 

This film gets 5.2/10 on imdb from 18000 votes. 

I haven't seen it, so no opinion from me. 

I see that Hannah Grace was played by a dancer/contortionist, is this part of what freaked you out - lots of scary body twists without obvious special effects?  

There were lots of these and the film was set in a morgue which isn't cricket either imo!

Apparently entirely shot on a Sony A7xx camera (where "xx" is the model variant, presumably the most modern one but still a consumer camera)