Callback ID lost while using the webview

This is a licensee UDN: [Link Removed]

I've reviewed the javascript/native bridge code and I don't see anything obvious.  The fact that it can happen on both mobile platforms might point at some higher level code issue vs the native interface for each platform. 

From the Licensee:

We are currently shipping a game using the 4.27 version of UE and are experiencing some unexpected behavior while using the webview on both Android and iOS. We have some "simple" UE objects from which some methods are being called from the webview (ie. from its JS code) and, from times to times, UE is raising an error saying "Unknown callback ID {callback ID}".