There are a number of things you can do make RF comms more reliable. The first things I would recommend is a preamble, and a good 'start of data' byte.

This is what I use for my RF projects:

Serout2 rf_pin,17197,[$55,$55,$66,data]

and

Serin2 rf_pin,17197,[wait ($66),data]

The $55,$55 is the preamble, and the $66 byte tells the receiver that the next byte(s) are the data.

If you want to get more fancy you can add manchester encoding/decoding subroutines.