@ben, thank you for supporting MAKERbuino and I am sorry for the problems that you’re experiencing with those units.
The power issue sounds like it must be related with the power circuit, did you try resoldering that part too?
Also, did you test the battery for some signs of unregulated 3.7V voltage before the regulator?
About the ones you cannot figure out - please get in touch via private messages or email (firstname.lastname@example.org) and we’ll help you fix them.
Where are you located? We can most likely arrange free shipping slips for you.
Also, we’d like to get in touch with you and see the workshops that you’re making. If you have some photos that you can share with us, we’d love to share them on our social media channels