Ok, at least one “bug” so far in the bed level visualizer. If the measured value is above 10 (or something in that neighborhood at least), I get the endless loading screen.
So this:
Send: M420 V
Recv: Bilinear Leveling Grid:
Recv: 0 1 2
Recv: 0 +17.042 +17.024 +17.056
Recv: 1 +17.405 +17.510 +17.776
Recv: 2 +17.014 +17.409 +17.840
Recv:
Recv: Subdivided with CATMULL ROM Leveling Grid:
Recv: 0 1 2 3 4 5 6
Recv: 0 +17.04250 +17.03435 +17.02620 +17.02375 +17.03079 +17.04352 +17.05625
Recv: 1 +17.19125 +17.19312 +17.19499 +17.20760 +17.23809 +17.27932 +17.32056
Recv: 2 +17.34000 +17.35189 +17.36377 +17.39144 +17.44539 +17.51513 +17.58486
Recv: 3 +17.40500 +17.43403 +17.46306 +17.51000 +17.58681 +17.68153 +17.77625
Recv: 4 +17.33042 +17.38846 +17.44650 +17.51977 +17.61840 +17.73226 +17.84611
Recv: 5 +17.17208 +17.26627 +17.36045 +17.46426 +17.58411 +17.71358 +17.84305
Recv: 6 +17.01375 +17.14407 +17.27440 +17.40875 +17.54981 +17.69491 +17.84000
Recv:
Recv: leveling ON
Recv: echo:Bed Leveling ON
Recv: echo:Fade Height OFF
Recv: ok
results in the endless loading loop and this:
Send: M420V
Recv: Bilinear Leveling Grid:
Recv: 0 1 2
Recv: 0 +8.490 +8.435 +8.379
Recv: 1 +8.736 +8.875 +8.989
Recv: 2 +8.491 +8.839 +9.108
Recv:
Recv: Subdivided with CATMULL ROM Leveling Grid:
Recv: 0 1 2 3 4 5 6
Recv: 0 +8.49000 +8.47171 +8.45342 +8.43500 +8.41634 +8.39755 +8.37875
Recv: 1 +8.59028 +8.59359 +8.59689 +8.59931 +8.60023 +8.60025 +8.60028
Recv: 2 +8.69055 +8.71546 +8.74036 +8.76361 +8.78411 +8.80296 +8.82181
Recv: 3 +8.73625 +8.78343 +8.83060 +8.87500 +8.91477 +8.95176 +8.98875
Recv: 4 +8.69097 +8.76155 +8.83213 +8.89819 +8.95672 +9.01072 +9.06472
Recv: 5 +8.59111 +8.68578 +8.78044 +8.86847 +8.94544 +9.01578 +9.08611
Recv: 6 +8.49125 +8.61000 +8.72875 +8.83875 +8.93417 +9.02083 +9.10750
Recv:
Recv: leveling ON
Recv: echo:Bed Leveling ON
Recv: echo:Fade Height OFF
Recv: ok
just works.
(yes, I followed the printhead around with a piece of metal to get that first measurement 
)
So that points to a bug in the bed level visualizer (didn’t go looking in the code yet). Even though I have the graph Z-limit set to 20 in the config.
I noticed that in one of your previous posts you had values >15 so that might be the reason why you’re getting the infinite loading screen.
edit: the magic number seems to be 10, this one doesn’t work anymore either:
Send: M420V
Recv: Bilinear Leveling Grid:
Recv: 0 1 2
Recv: 0 +8.490 +8.419 +10.171
Recv: 1 +8.739 +8.872 +10.865
Recv: 2 +8.502 +8.851 +9.120
Recv:
Recv: Subdivided with CATMULL ROM Leveling Grid:
Recv: 0 1 2 3 4 5 6
Recv: 0 +8.49000 +8.39870 +8.30741 +8.41875 +8.86782 +9.51954 +10.17125
Recv: 1 +8.59088 +8.51910 +8.44732 +8.58759 +9.08130 +9.78706 +10.49282
Recv: 2 +8.69176 +8.63949 +8.58722 +8.75643 +9.29477 +10.05458 +10.81440
Recv: 3 +8.73875 +8.71449 +8.69023 +8.87250 +9.39898 +10.13199 +10.86500
Recv: 4 +8.69593 +8.71383 +8.73173 +8.90060 +9.32108 +9.89253 +10.46398
Recv: 5 +8.59921 +8.66777 +8.73633 +8.87593 +9.13392 +9.46295 +9.79199
Recv: 6 +8.50250 +8.62171 +8.74093 +8.85125 +8.94676 +9.03338 +9.12000
Recv:
Recv: leveling ON
Recv: echo:Bed Leveling ON
Recv: echo:Fade Height OFF
Recv: ok
edit2:
So I assume there is some regular expression parsing the data that expects only one digit before the decimal point. But my python isn’t great so can’t put my finger on it yet. (And I hate programming languages that use whitespace as a part of the language…) It would have helped if it was somewhat documented in code as well.
Will you file the bug at bedlevelvisualizer? 