Profile photo of Biggsounds

When you say failing do you mean the app crashes, or simply disconnects? If it’s disconnecting constantly you’ve probably got an IP conflict on your system. Check that your router & all the associated parts of your system are addressed correctly as per the suggestions on the reference guide (available via the Allen & Heath site downloads page),
Alternately you may have a dodgy download (particularly if, as suggested, it’s kicking you off without even connecting to a network) – it’s been the cause of problems for users elsewhere on the forum. Try uninstalling it & download it again, also close everything in the background to make sure it’s not a memory issue on the phone.
I use Tweak all the time (and on a lowly 3GS) & never have any such issues, so I don’t think it’s the software.

iDR32 mixrack
MixRack for iPad & Tweak for iPhone apps
Asus N61 Laptop (x2 wireless)
Sennheiser IEM (for PFL)
Dante card (soon!)