I don't think it's an anti-recording device.
Could just be the SCART lead needing reseating in the sockets on the Sky/Sony boxes - do you use any SCART switching as they can be a problem?
Or it's the software/firmware in your Sony box. Have you looked for any firmware updates? Usually you download to your PC then burn to a CD - then place the CD in the Sony and it should auto update.
My experience of DVD/HDD recorders suggests they aren't as simple or as reliable as VCR's. I occassionally find a blank recording after setting up the DVD/HDD timer correctly. Not sure if it's the DVD/HDD or satellite box but suspect the DVD/HDD!