You Database administrator should be able to find out the query behind the session blocked.
This could be helpfull to find what application lock the database.
I suggest also to review your scripts and add a DISCONNECT; instruction at the end of your scripts and before every new connection to clean your scripts.
Another tip from my Qlikview Experience.
Using include instruction we exported every qlikview scripts in a QVS files named as the report.
That way we are able to search for query/instruction/connection through evey scripts in few seconds using Notepad++ or Sublim Text.
I'll try to write a post on QlikCommunity to talk about this.