Problem choosing selected file

Im not sure what it is you mean here, and its not clear from your attachments unfortunately. Im not having any issues on this end with selecting and adding existing attachments

This button disappears as soon as you select any attachment

I’m not able to replicate that issue on my end. What device and browser are you using there?

Changed Status to Awaiting Feedback

I'm not able to replicate that issue either.

The problem appears on mobile only

Im not seeing this on mobile either. Could you let me know what device and browser you are using?