WinAppDeployCmd: 0x80131500 - Failed to copy package: Unspecified error

I'm trying to deploy my work-in-progress app to my Lumia 435 Windows Phone (Win 10, build 10.0.14393.576) using WinAppDeployCmd. I'm quite new at this and keep getting the following errors:

Installing app...Disconnecting. 0x80131500 - Failed to copy package: Unspecified error 'Microsoft Corporation' violates pattern constraint of '\bms-resource:.{1,256}'. 0x80131500 - Unspecified error 'Microsoft Corporation' violates pattern constraint of '\bms-resource:.{1,256}'. 0x800700E8 - Unspecified error 'Microsoft Corporation' violates pattern constraint of '\bms-resource:.{1,256}'.

My PC and phone are both in Developer mode and the phone is successfully paired.

I'm still in development so frequently deploy the app to my phone for testing. I've done so successfully several times. Recently there was a Windows phone update to build 10.0.14393.576 which I installed, after which this problem started happening. Could someone help explain:

a) Could the update be the issue?

b) What 0x80131500 - Failed to copy package: Unspecified error means, or where to get information about such error codes?

c) What can I try to resolve this?

This is a cross post as I've had no answers on another forum. Thanks.