Do you have a read-only link available for the project that you can include for us to take a look at? I’ve personally never tried adding sticky elements within a tab, however I don’t see why it wouldn’t be possible.
So I just tested this myself and confirmed it doesn’t work due to the default overflow: hidden setting on the .w-tab-content element:
Removing this setting fixes the issue and allows for sticky positioning, however I can’t say whether or not this will cause issues with functionality of the tabs themselves in the long run.
You can see it working on my example below, and thankfully I don’t see issues in my (limited) testing: