Unexpected minor tick on QwtPlot x axis

[vix]

I try to do my best in the next few days to get a small example.
In the meanwhile I can add some additional info and a screenshot.
capture.PNG

If you keep running the time series you see that the "artifact ticks" come in small groups of three of them.
You can also see that their size is smaller than the size of the major tick, and the central one in longer than the two side ticks.
But all of them are shorter than the major ticks.

The number of these "groups of ticks" is 5, and 5 is the number of the major ticks I set.
Even if I keep running the time series, after 5 groups no more artifact ticks appear.


Maybe this can help, maybe it can't.