I made some Arduino shields for nRF24L01+ modules and I have interesting problem:
If I have modules directly connected to the shield (pinhead on module to socket on shield), there is high packet loss (about 20-30%) when sending data to another nRF module. But, if I touch the module antenna by my hand OR modules are connected to this shield by wires (cca 10cm), all works ok.
I use these nRF modules:

Any idea what can cause this problem?

