Hi, I’m facing something similar and found this thread.
These issues are common to many webapps / hybrid apps and there are many reasons behind that “slow response” you get here and there.
As a general workaround I would suggest using a loading spinner (ie https://ionicframework.com/docs/api/components/loading/LoadingController/) to notify the user that something is going to happen and then dismiss once the “long” operation has completed.
In more detail the “present” method of the LoadingController is a promise therefore you can wait for the loader to appear (this gives a quick feedback to the user) and after that you can launch the “long” operation.
Hope it helps!