Retrospective record buffer preference keeps resetting


I have Cubase pro 10.5.10 build 120

The default for midi retrospective record buffer is 10,000 events which isn’t enough for me, so I have set preferences to the maximum 100,000 events.
But a couple of days later it is back to 10,000.

[edit It is in fact after every restart of cubase.]

Has anybody else experienced this? Why does it do this?