The value axis unexpectedly changes its visual range when you begin zooming and doesn't allow you to zoom out of this range. The cause of this behavior is an asynchronous data source.
I reproduced it in this demo.
dxChart - Value axis zooming is broken if a data source is asynchronous
Answers approved by DevExpress Support
We have fixed the issue described in this ticket and will include the fix in our next maintenance update. To apply this solution before the official update, request a hotfix by clicking the corresponding link for product versions you require.
Note: Hotfixes may be unavailable for beta versions and updates that are about to be released.