Steps to reproduce:
1) On campaigns list (/admin/{orgId}/campaigns), click + button.
2) Fill in Basics, Contacts, Texters sections, until all are green.
3) Under Interactions, add "hi {firstName}" in script input, nothing else.
4) Save Interactions section.
5) Open another section, then go back to Interactions.
6) If Interactions isn't yet empty, repeat steps 3-5.
When this happens, the Interactions section looks like this:

Then it's impossible to add steps to the interactions. The only option is to archive the campaign and start over.
This occurs because if theres any way that the original interaction is deleted but nothing is saved in its place then the form goes screwy. A good way to solve this is on the backend if interaction steps ever returns nothing then it should send a fake new interaction step in its place to the client. Ie the server ahould always send something
@sreynen @schuyler1d I could take a look at this one!
@schuyler1d is this still true?
@ibrand just tried these steps and the bug isn't coming up for me!
confirming with @schuyler1d?
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@sreynen @schuyler1d I could take a look at this one!