Seems to me like PoweRec is kicking in, this is quite normal for the PX-716A. If you can (and want to waste a disc), use Nero CD-DVD Speed and do a Create Data Disc test. This will actually record a disc and show you the exact speeds the drive is recording at. It will hopefully also produce the speed drop. Then, once it is done you can save the results and post it here. Also, if you can waste another disc, disable the PX-716A's PoweRec function and perform another Create Data Disc test via Nero CD-DVD Speed. PoweRec can be disabled via the PlexTools software. Once PoweRec is disabled you probably won't see the drop in recording speed (although this is now always preferred because PoweRec reduces the write speed for a reason: reducing write errors). Let us know what you find out.