I have noticed that all versions of XForms above 188.8.131.52 have introduced 'lag' when switching between Master-Detail pages. The navigation menu slides away, but then the page goes white for a few seconds before loading with a little animation. Previously, the page title would update immediately after selection and page content soon after that.
Having a look at the release notes between 184.108.40.206 and 220.127.116.11 I found this,
- Isolate fragment management for children of MasterDetailPage. If an AppCompat MasterDetailPage hosts NavigationPages or TabbedPages in either the > Master or Detail sections, those pages are now wrapped in their own Fragment (and use that Fragment's ChildFragmentManager) to isolate their Fragment management operations and avoid recursive entry into the executePendingTransactions() method. Also fixed a disposal bug in the custom MDP renderer in Control Gallery. [see 40333, 40639]
Maybe there is some kind of fragment animation taking place?