Publish / Modify forked iOS open source app

Hello,

I am looking for someone to help me publish a forked open source app.
https://github.com/haiwen/seafile-iOS

We were already able to publish the app in testflight, however when we install the app from testflight on an iPhone, the app crashes right after login.
In the simulator, however, the app runs without problems.

I pulled this from the crash log:

Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY
Triggered by Thread: 0

---

Thread 0 crashed with ARM Thread State (64-bit):
x0: 0x0000000000000000 x1: 0x0000000000000000 x2: 0x0000000000000000 x3: 0x0000000000000000
x4: 0x0000000198ea80ad x5: 0x000000016f4bdf50 x6: 0x000000000000006e x7: 0x0000000000001900
x8: 0xe837cdba55b775de x9: 0xe837cdbb5571b05e x10: 0x0000000000000002 x11: 0x000000000000000b
x12: 0x0000000091a3e004 x13: 0x0000000011a3e000 x14: 0x0000000000000010 x15: 0x0000000000000002
x16: 0x0000000000000148 x17: 0x0000000100c6c580 x18: 0x0000000103482260 x19: 0x0000000000000006
x20: 0x0000000000000103 x21: 0x0000000100c6c660 x22: 0x0000000000000000 x23: 0x0000000283972b70
x24: 0x0000000000000000 x25: 0x0000000100c6c660 x26: 0x0000000280f49fc0 x27: 0x000000000000000f
x28: 0x0000000002ffffff fp: 0x000000016f4bdec0 lr: 0x00000001f0f39378
sp: 0x000000016f4bdea0 pc: 0x00000001b7a9b964 cpsr: 0x40000000
esr: 0x56000080 Address size fault