Hello @L !
Thanks for reporting this bug to us!
We’ve reported this issue to our developers so they can work on a solution right away. We will make sure to update this topic as soon as we have news about this, and of course we'll do our best to fix this as soon as possible 🌈
As @John Do mentioned, a workaround is to type the name of the sub-account, or going to the sub account and tapping on 'Add money+' > Add from sub-account