- changed the scaling for the three Y-axis from 820, 820, 8.20 to 870, 870, 8.70
- no other changes made
- the Y axis' all display correctly now (correct.jpg)
Both charts had three Y axis'.
Both charts exhibited the issue on Y-axis 1.
Both charts had the Y axis 1 low at 0, and the high at either 830 or 820.
Edit: further update
- returned Y-axis to 820, 820, 8.2 to check
- now the charts correctly at the old setting
- looks like this issue will get corrected only under a most fortuitous accident