That is not normal behavior. Please do the following checks one by one:
#1) Do this and only keep the Stripe payments and Stripe Subscriptions addon active:
Test for Plugin and Theme Conflict Before Posting an Issue or a Bug
#2) Go to the settings menu of the Stripe payments plugin and enter both the Live and Sandbox API keys. Save it. Go back to the settings page to reload the page and check if those API key values are in there (meaning those are properly saved in your site)
#3) Go to the Settings -> Subscriptions tab and then use the “Clear Cache” button (if it is available). Also use the “Delete Webhook” (if the button is there). This is to make sure everything is clean.
#4) Go back to the Settings -> Subscriptions tab and try to create new webhooks.
Can you see the webhooks being created correctly there?