Xcuitest, xcode 8, ruby_lib 8.0, iphone9 ios 10 set_context failing for webview

Portion of log of interest:

[debug] [RemoteDebugger] Checking document readyState
[debug] [RemoteDebugger] Sending javascript command (function (){ return docume…
[debug] [RemoteDebugger] Sending ‘_rpc_forwardSocketData:’ message to remote debugger
[debug] [RemoteDebugger] Received applicationSentData response
[debug] [RemoteDebugger] Found data handler for response
[debug] [RemoteDebugger] Received data response from socket send: ‘complete’
[debug] [RemoteDebugger] Original command: sendJSCommand
[debug] [RemoteDebugger] readyState was “complete”
[debug] [RemoteDebugger] Page is ready
[MJSONWP] Responding to client with driver.setUrl() result: null
[HTTP] <-- POST /wd/hub/session/1c9b8fcc-7fd8-4138-9775-e2f5f138e04a/url 200 3542 ms - 76
[HTTP] --> POST /wd/hub/session/1c9b8fcc-7fd8-4138-9775-e2f5f138e04a/context {“name”:“WEBVIEW_1”}
[MJSONWP] Calling AppiumDriver.setContext() with args: [“WEBVIEW_1”,"1c9b8fcc-7fd8…
[debug] [XCUITest] Executing command ‘setContext’
[debug] [iOS] Attempting to set context to ‘WEBVIEW_1’
[HTTP] <-- POST /wd/hub/session/1c9b8fcc-7fd8-4138-9775-e2f5f138e04a/context 500 2 ms - 109
[HTTP] --> GET /wd/hub/session/1c9b8fcc-7fd8-4138-9775-e2f5f138e04a/screenshot {}
[MJSONWP] Driver proxy active, passing request on via HTTP proxy
[debug] [XCUITest] Executing command ‘proxyReqRes’
[JSONWP Proxy] Proxying [GET /wd/hub/session/1c9b8fcc-7fd8-4138-9775-e2f5f138e04a/screenshot] to [GET http://localhost:8100/session/2D1E4596-2805-42A1-AA61-1829D91DD472/screenshot] with body: {}
[debug] [RemoteDebugger] Checking document readyState

Simulator and safari launches fine

Problem is with each session the webview value keeps changing for e.g. WEBVIEW_8090.1, WEVIEW_8367.1 etc