Crash on ios 12.1.3 because of metal

Hi there, I have recently tried to update my iOS app which is already in the app store. Now I have built my game successfully, uploaded it to testflight, and testet it on my iPhone 8 on 12.0.1. After sending the app to apple for review I got rejected because it crashed on their iphones. I have read the log and the crash appeard on iOS 12.1.3 (which i hav NOT tested on). Now it seems that it has to do something with METAL Rendering but I have no clue what to do! Very frustrating. This is my edited crashlog I got from apple: (I edited some info for privacy sake)

{"app_name":"IOSEZY","timestamp":"2019-01-23 07:50:16.78 -0800","app_version":"1.0.117","slice_uuid":"xxxxx","adam_id":1395389722,"build_version":"0.1286","bundleID":"com.xxxxx","share_with_app_devs":false,"is_first_party":false,"bug_type":"109","os_version":"iPhone OS 12.1.3 (16D39)","incident_id":"19C878EC-7681-4CE6-8030-FA84D2AE6E35","name":"IOSEZY"}
Incident Identifier: 19C878EC-7681-4CE6-8030-FA84D2AE6E35
CrashReporter Key:   xxxxxxx
Hardware Model:      xxx
Process:             IOSEZY [628]
Path:                /private/var/containers/Bundle/Application/FAFFB577-66E0-4696-9626-A703440429C0/IOSEZY.app/IOSEZY
Identifier:          com.xxxxx
Version:             0.1286 (1.0.117)
AppStoreTools:       10B63
Code Type:           ARM-64 (Native)
Role:                Non UI
Parent Process:      launchd [1]
Coalition:           com.xxxxx [584]


Date/Time:           2019-01-23 07:50:16.5741 -0800
Launch Time:         2019-01-23 07:49:51.0229 -0800
OS Version:          iPhone OS 12.1.3 (16D39)
Baseband Version:    7.32.00
Report Version:      104

Exception Type:  EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note:  EXC_CORPSE_NOTIFY
Triggered by Thread:  2


Thread 2 name:  Dispatch queue: com.Metal.CompletionQueueDispatch
Thread 2 Crashed:
0   libsystem_kernel.dylib        	0x00000001bf05f104 0x1bf03c000 + 143620
1   libsystem_pthread.dylib       	0x00000001bf0db020 0x1bf0d9000 + 8224
2   libsystem_c.dylib             	0x00000001befb6d78 0x1bef5f000 + 359800
3   IOSEZY                        	0x00000001017dab24 0x100da0000 + 10726180
4   IOSEZY                        	0x00000001018ca910 0x100da0000 + 11708688
5   IOSEZY                        	0x000000010188d818 0x100da0000 + 11458584
6   IOSEZY                        	0x0000000101744bb0 0x100da0000 + 10111920
7   IOSEZY                        	0x000000010175b430 0x100da0000 + 10204208
8   IOSEZY                        	0x0000000101744160 0x100da0000 + 10109280
9   IOSEZY                        	0x0000000101744030 0x100da0000 + 10108976
10  IOSEZY                        	0x0000000101744c5c 0x100da0000 + 10112092
11  IOSEZY                        	0x0000000101209aec 0x100da0000 + 4627180
12  Metal                         	0x00000001c167dc58 0x1c1618000 + 416856
13  Metal                         	0x00000001c167f1f4 0x1c1618000 + 422388
14  Metal                         	0x00000001c16285e0 0x1c1618000 + 67040
15  Metal                         	0x00000001c1683bd0 0x1c1618000 + 441296
16  Metal                         	0x00000001c1651350 0x1c1618000 + 234320
17  IOAccelerator                 	0x00000001c160f164 0x1c160c000 + 12644
18  IOKit                         	0x00000001bf728b24 0x1bf723000 + 23332
19  IOKit                         	0x00000001bf728bb4 0x1bf723000 + 23476
20  libdispatch.dylib             	0x00000001beebab58 0x1beea1000 + 105304
21  libdispatch.dylib             	0x00000001bef02484 0x1beea1000 + 398468
22  libdispatch.dylib             	0x00000001beea582c 0x1beea1000 + 18476
23  libdispatch.dylib             	0x00000001beeb5b9c 0x1beea1000 + 84892
24  libdispatch.dylib             	0x00000001beea9a9c 0x1beea1000 + 35484
25  libdispatch.dylib             	0x00000001beeaa718 0x1beea1000 + 38680
26  libdispatch.dylib             	0x00000001beeb2eb8 0x1beea1000 + 73400
27  libsystem_pthread.dylib       	0x00000001bf0e50dc 0x1bf0d9000 + 49372
28  libsystem_pthread.dylib       	0x00000001bf0e7cec 0x1bf0d9000 + 60652

Please any help from someone who knows how to solve this. I will try to use UE4.21 but it is such a hassle to transfer it again. There must be something wrong with metal can i fix it by editing something?

according to apple the app runs on an iPhone 6s(don’t know why they mentioned that) but it crashes on the iPad Air. They did not state iPad Air 2, therefore I think it has to do something with the model from 2013. That one has Apple A7 processor just like the iPhone 5s - but it does not crash on that device! Someone please help