Most of the work Movie Edit Pro (17.0.2.159) gets here is cutting ads out of movies I have recorded from free-to-air TV 😉. It's nice and quick when I am finding and selecting the offending frames, but it can take minutes to delete them. It was the other way round with my old (ten years or more) version. What's wrong?

Is there some setting I might have incorrect?

My machine is Intel QuadCore i5-3470 CPU @ 3.20GHz, 32 GB RAM, running MS Windows 10 Home on an MSI B75MA-P45 motherboard.
It was assembled by Net Solution Computers of Morley, Western Australia, and has a SAMSUNG U28D590D VDU driven by an NVIDIA QUADRO K620 Video Card and RealTek High Definition Audio.
I have Windows Defender and Malwarebytes as Anti-virus with Firefox and Skype running in the background.