Fenix 3 FW 8.70 crashes with my app

I have several users reporting full system crash when using my Tabata app (https://apps.garmin.com/en-US/apps/5...0-8f85f0dea6e8) on Fenix 3 with fw 8.70 ( and earlier versions). I have got some ERR_LOG files from a friend doing some beta testing and I can'r figure out what is going on.
Using the latest release app (apparently recompiled? by Garmin) he gets this:
2050 (fenix 3) SW ver: 870
Build Type: RELEASE
Battery Voltage: 4.128000V
01/25/18 21:36:29
RTL
errnum: 0x002
r0: 0x20022be8
r1: 0x00000007
r2: 0x00034891
r3: 0x00000000
Return Address (LR): 0x000a817b:Call Stack - PSP at 0x200229e8:
0x00123eeb
0x000a817b
0x00034891
0x0000e069
0x00034891
0x00034891
0x000348e1
0x0011ff39
0x00121691
0x00121877
0x00159de5
0x000a7ebd
0x000a7ebd
0x0012768f
0x000a7ebd
0x000a7ebd
0x000a8729
0x000a8729
0x001279ad
0x00160403
HWM_usb_connected = 0x00. HWM_usb_mode = 0x01.
page addr = 0x001216b5
page addr = 0x000ee279
Uptime: 952941


If i rebuild using the latest SDK 2.4.2 and set min version to 1.4 it also craches:
2050 (fenix 3) SW ver: 870
Build Type: RELEASE
Battery Voltage: 4.096000V
01/25/18 21:06:54
RTL
errnum: 0x002
r0: 0x20022be8
r1: 0x00000060
r2: 0x000fd41f
r3: 0x00000000
Return Address (LR): 0x000a817b:Call Stack - PSP at 0x20022868:
0x000a817b
0x000fd41f
0x0000e1b5
0x000fd41f
0x000fd41f
0x00039807
0x000a7ebd
0x000a7ebd
0x000a7ebd
0x000a8729
0x000a7ebd
0x000a7ebd
0x000a8729
0x001251f3
0x000a8729
0x0005c7eb
0x000a8729
0x0005c88f
0x00030003
0x00030003
HWM_usb_connected = 0x00. HWM_usb_mode = 0x01.
page addr = 0x001216b5
page addr = 0x001216b5
page addr = 0x000ee279
Uptime: 37836714


In the simulator and on Fenix3HR FW4.70 everything works just fine. Please help sine I will have to remove Fenix3 from supported devices if this continues..