I have used these extensively (although I get mine direct from WenShing in Taiwan). These are superregenerative ASK receivers. They need a pronounced preamble in order to set the AGC and receive threshold. They work quite well at low data rates using a protocol like the NEC protocol (used by X10 for their wireless remotes) which I've detailed here...You might also benefit from reading this page...You need a fairly good balance between pulses and spaces (which Manchester encoding guarantees) but the fact that you need to send several copies in order to receive reliably indicates you need the initial copies to set the threshold and AGC.
Which output pin are you using? Using the linear (analog) output can complicate things. It's usually best to use the digital output. A good receiving antenna is important. An eggbeater is easy to build and matches the 50-ohm input impedance of the receiver.You can capture the output(s) from the receiver using a soundcard as I show here...which can give you an idea of the quality of the signal as received.
Bruce Reynolds sells the 433.92MHz version of this receiver. I believe he has some example projects with PBP code on his website.
BTW, the fact that your code works with a hardwired connection is another indication that your problems are related to RF signal quality.
Good luck.
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