1. we had many incidences of exactly the same problem earlier in the piece. Like you, we swapped pulses, we changed from fingerclip to earclip etc etc. It would work once or twice, then fail. Eventually, we discovered two fixes, and now our Pulse works every time.
(1) Our USB connection must be perfectly stable. We leave our pulse plugged in all the time now using the short USB stick rather than the cable. We're careful not to jolt it, or allow it to "droop". We've become very precious about it!
(2) We use the earclip every time now, but before clicking "scan" we check that the red pulse light is relatively consistent, i.e. not flashing erratically. We move the clip around the ear until we get it right, then click scan.
They are simple things, but we now have success every time. Given that we do at least three scans every four days, that's pretty good.
2. I also have had a similar problem. My USB was problematic but I sprayed into the connection on the computer with an electronic connection spray - like WD40 but for electronics. That resolved most of that issue.
I could not get a good pulse from the finger connection and, like you, have swapped to the ear clip which seems to work OK for me.
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