A generic comment on the topic title and the statement
Do you remember what AUR is an acronym for?
Arch User Repositories.
AUR is available but unsupported and in some cases it requires Manjaro Linux unstable branch to be on par with Arch Linux libraries.
While pamac has the ability to rebuild custom packages - does it work? - that depends on the maintainer of the script in question.
Yes, you are.
- Failing to check the comment trail for the custom script(s) on AUR
- Assuming that Manjaro endorse the use of AUR
- Assuming the availability implies a continued stability on Manjaro
- Assuming Manjaro is responsible for the quality of a custom script
What you can do to rectify