Hi lordsmurf, thanks for your reply. Sorry for following up so late.
Below is a screen capture of the noise:
The left-hand side is a frame from the first time I did a capture. I played back the first 2 minutes of this time a few times consecutively. On the right-hand side you see the same frame from the fourth capture. I believe the noise gets worse with time.
I've also posted a video of the capture with the SL-HF950 here
For comparison, I've posted a video of the same segment captured with an SL-F35
It seems the white noise areas in the SL-HF950 capture are not affected in the SL-F35 capture. The SL-F35 instead introduces black stripes at high-contrast transitions.
What should I do to play back these tapes with minimal noise?