Thanks for your efforts.
Don't think I'm not quite happy with it because overall I am, I'd have got, or swapped it for an X with free (but never to be used decoding) or something else if I wanted. I think the low noise on 10mV/5mV/2mV is excellent.
I'll have to post a couple of full size screen captures.
HW B-64-5.1
I've put the trigger level right on the border of triggering/not triggering as shown by the trigger counter showing 530Hz, a pixel or 2 up or down would change it to <10Hz or 1.000kHz, and obviously I can see when the waveform is alive or dead.
I'd like to say a self-calibration fixed it but it didn't.
Persistence captures didn't save, I'll try again. - Done.
If just a single channel is ON, then persistence is missing from 50ns as well.
Persistence:
Missing persistence (50ns) feels like bug in FW what you use.
If I remember right (long time ago when last used CML model) when scope is stopped, persistence disappear but if save screen image "on fly" it also save persistence.
Trigger:
It looks normal (with this your single example and explanation).
It need understand and remember that this model do not have full digital trigger system. It is very different what can find in example SDS1000X and 2000X and many other modern technology scopes what have full digital trigger system and what make them totally different animals.
For CML and CML+ specifications tell (only) trigger sensitivity (what is perfect definition for this?)
Trigger Sensitivity:
1 Divisions: DC-10 MHz
1.5 Divisions: 10 MHz - Max BW
In this model (Whole SDS1000 series) trigger system is traditional old two analog pathway system. Simplified: Analog signal is splitted for trigger system after final buffer amplifier before ADC. Then routed and level edjusted to analog trigger comparator. Comparator other port have this analog signal. Then there is system generated (DAC + some adjustments) trigger level. When it cross this level comparator output change and this signal is binary trig signal. (this is also what counter counts, in principle).
Digitized analog signal what is displayed on the screen is not signal what trigger comparator get. There is many small differencies due to different analog signal handling, trigger comparator hysteresis (what is very important) and this signal also include different signal noise, different bandwidth shape, inaccuracies and noise in trigger level signal. Also trigger comparator is not school book ideal component.
As can see in image it do not generate trigger signal after every rising edge. Because your trigger level setting is just borderline if it can see this edge or not. It really need realize that on the screen is signal what human look with eyes but it is not what trigger comparator see. Also there need be hysteresis. Comparator need see that after every rising edge what crosses hysteresis upper level is then returned down and reliable below hysteresis lower level. Both of these must happen. But on the screen we can not see real this signal what trigger comparator see and what is see in its other port for compare.
Of course this kind of system is possible to do very accurate but after then we do not talk simply cheap machines. (analog pathway trigger can be, if really do "rocket science" very advanced...(because analog processing is fast, because analog processing do not drop to Nyquist-Shannon trap etc. But extremely good analog pathway trigger system in fast digital advanced oscilloscope is - expensive and complex. I'm not ssure but perhaps example LeCroy have done there some experimental things...)
Shortly: With this kind of trigger system this (what you explain with this one image) is just normal. It is how it works. Important is: "know your equipment" limits.
Many times (but not always) and example in this case, just push trigger level button for autoset half level trig and you get quite reliable trigger and right counted trigger pulses for frequency counter)
(Why I can say it is normal (if look this one example).
I have tested "lot" of individual SDS1000CML and CNL models. (Not this new CML+)) Also I have tested many individual older Rigol DS1000E series (what have same trig principle) and also example lot of some older Owon models and even in bottom some Hantek models. I have used "truck load" of some older Tektronix and HP digital scopes what also have same trigger principle but more expensive and mostly better - if not look this one "famous" total junk Tek "school" model. (and of course even more both of these analog scopes - and still in use)
In full digital trigger system all is different. (simplified principle) Trigger system "look" same digitized signal after ADC what we look on the screen. What is digitized is what trigger system see (but it also see only this)
Take this seriously. Remember that all you see on the scope screen is sum of all kind of errors mixed with undefined true signal. Never you can see there whole pure truth and only this. Independent of if your scope price is $100 or $100000.