Nested Parent Tab freezes with addition of child tabs

### Version
Tell us which versions you are using:

- react-native-router-flux v4.2.0
- react v16.9.0
- react-native v0.?.? - https://github.com/expo/react-native/archive/sdk-37.0.1.tar.gz

### Expected behaviour
I should be able to click both Parent Tabs and Child Tabs
since Ive created a tab component inside another tab component.

### Actual behaviour
My parent tab component freezes while my child tab component
can switch between both tabs

### Steps to reproduce
For non-obvious bugs, please fork this component, modify Example project to reproduce your issue and include link here.
1. Create a Router and Scene tabbar with two tab components "Cloud" and "Settings"
2. Create a Router and Scene tabbar with two tab components inside "Home" - "LiveChat" and "Posts"
3. You can no longer switch between "Cloud" and "Settings" as that tab is now frozen

### Reproducible Demo

Please provide a minimized reproducible demonstration of the problem you're reporting.

Ive included pictures in case Im messing up something simple. Heres the "Parent Tab" where "CloudsTab" and "SettingsTab" are the two tabs.

Heres the child tab where "Live Chat" and "Posts" are the two child tabs - these work.

And heres the iOS print screen. Also happening on my Android phone

Is this feature not supported, is this a bug, or dumb mistake on my part?
Ive tried taking out Router in the child tab and some other things but none work.

Issues that come with minimal repro's are resolved much more quickly than issues where a maintainer has to reproduce themselves.