Lessons of the First ones should be repeatable

Repeatable. You can gain this invocation more than once. Each time you do so, choose a different Origin feat.

But the builder doesn't allow it to be taken multiple times

I had to manually add the origin feat.  This should be a simple fix for them.  

Also experiencing this issue

This has been the case since the 2024 information has dropped.
Can confirm, will not allow for multiple selection of this invocation.

plz fix these bugs!!!!!!!!!!!!!!!!!!!!!!

I would like to use this correctly in the UI so it is clear I haven't added feats I shouldn't have when the DM looks at my character.

Ya dnd beyond needs to fix this and make custom background easy and convinient.