Thanks for your report. Just to be completely clear.... you did try the following?
1. Display a signal on CH1 from the probe Calibrator, at 1V/div, trigger type Edge, trigger level 2.00 V, sweep mode Auto
2. Set Horizontal Scale to 1 us/div
3. Select "Auto" from Acquire>Mem Depth menu
4. Select "100 ms" from Display>Persis. Time menu
5. Enter Horizontal Zoom mode by pressing the Horizontal Scale knob
Yeah, checked it again using that exact sequence and all I can notice is a slight hesitation on the screen update when going into H Zoom mode. I did it 5-6 times and the behaviour seems consistent.
Looking at your video, using that sequence, it seems all the controls goes unresponsive but the scope it self is continuing to operate and updating the display with the waveform. So is something triggering the KeyLock feature? and is the KeyLock feature otherwise working normally? just a thought...
Thanks for checking again. This seems to confirm that the problem only affects some, perhaps half, of the scopes tested. That is really strange.
Yes, the scope continues to display a live waveform when the controls freeze.
The KeyLock feature seems to be working normally: When the KeyLock feature is set to "Lock" by the button in the Utility menu, pressing any key brings up a notice "Keyboard Locked!" But this notice does not appear in the "frozen" state when one presses a key.
Also, when the scope is "frozen" it does not respond to an attempt to connect via Telnet over the LAN.
When it is legitimately "locked" with the KeyLock feature it accepts a Telnet connection and responds to the :SYSTem:LOCKed? query and other SCPI commands and can be unlocked by sending the :SYSTem:LOCKed 0 command. If the scope is connected via Telnet and then the "freeze bug" is initiated while connected, the scope no longer responds to SCPI commands over the Telnet connection and cannot be unfrozen by the SCPI commands.
Also, I can "freeze" the scope by sending the appropriate SCPI commands over the Telnet connection, at which point it stops responding to the remote connection:
:DISPlay:GRADing:TIME 0.1
:ACQuire:MDEPth AUTO
:TIMebase:DELay:ENABle 1
-- and the scope freezes, stops responding to the Telnet connection, and requires a reboot. But it still shows a live waveform !!