Using hydration triggers "failed to copy cordova.js" error on iOS

[djipco]

I am using hydration during development to push test builds of an app to several iOS 12.3.1 devices (iPhone 5S). As expected, when the app starts on the device, I get asked if I want to update. If I click on "Update & restart now", it seems to download stuff (because I see the progress bar and it says "Retrieving new content") but at the end I get this error:

Whoops, looks like an error occured. 
failed to copy cordova.js

I can then press "Retry" as many times as I want but it simply does not work.

Edit: it seems this problem has been around for quite a while (2017): https://stackoverflow.com/questions/43982362/phonegap-build-failed-to-copy-cordova-js

[djipco]

If I completely uninstall the application and reinstall it, hydration works and I do not get the error.