Android System WebView 52.0 seems to cause a lot of issues in the applications based on webview.
SkyEpub strongly recommends developer to delete Android System WebView from devices which run Android 5.x,6.x or above.
The Stylesheet inside the epub files which are created by Sigil Editor conflicts Android System WebView 52.0

SkyEpub 6.2.9.1 added new function
public void setSigilStyleEnabled(boolean enabled);

this function will enable or disable the stylesheet of the epub which is created Sigil Editor to prevent conflicts with Android System WebView 52.0.