Appreciate all the links and information.
I just wanted to give an update about the cheap props I bought with locks installed. They look identical however I can attest to the quality control. I can however give feedback from todays flight.
Normally when I put mine on for a flight , I simply give the props a hard flick and then another once they find resistance - I'm not sure if it's because they have never been put on before, but the cheap ones from ebay did not seem to find the grove (lock in) as effectively as the originals - BUT - they did catch on/grab/and or fit into position - I simply held the motor in place and pushed them a little more to tighten them.
I have to say I was impressed at how smooth the drone was moving - All the same I was quite nervous as this flight test was over water at high tide. At the end of the flight all I can say is that I got lucky with the set I bought. Cost my $20.00 Au/aprox $18.00US for a full set.
IMPORTANT - I will note that I now understand how my friends could of come off ... I think the main issue with the flebay ones is to make sure you double check and perhaps give a slight push (only slight) by holding the motor to ensure they have locked on. Might sound like a hassle ... BUT ... for the price, I'm happy to give a little nudge ... and to be honest, I think once they have been on a few time like so, that they will actually grab a lot easier.
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I'm not saying there is no risk - totally agree that the quality control may be questionable ... just be sure to check manually after flicking the props on.
Early days yet, more flights to come.
If your not hard up with the $$$, then for sure go DJI, however if your game and don't mind having to double check ... I'm thus far happy to try another set.