MPU Fault on Downloader library although stack size is configured at maximum

Question

I am trying to use the AWS FOTA library. It correctly downloads the image at 100% but always ends with a MPU Fault on the downloader thread.

I set the stack size at the maximum value (CONFIG_DOWNLOADER_STACK_SIZE=8192) and it doesn't solve the issue.

[00:03:24.600,708] <inf> downloader: Downloaded 430848/430959 bytes (99%)
[00:03:25.757,324] <wrn> modem_cmux: Frame FCS error
[00:03:25.757,354] <wrn> modem_cmux: Dropped frame
[00:03:27.200,286] <dbg> net_if: net_if_tx: (rx_q[0]): Processing (pkt 0x200345fc, prio 0) network packet iface 1 (0x200038ec)
[00:03:27.200,408] <dbg> net_sock: zsock_received_cb: (rx_q[0]): ctx=0x20009308, pkt=0x2003497c, st=0, user_data=0
[00:03:27.201,324] <inf> downloader: Downloaded 430959/430959 bytes (100%)
[00:03:27.201,354] <inf> downloader: Download complete
[00:03:27.201,416] <dbg> net_sock: zsock_close_ctx: (downloader): close: ctx=0x20009308, fd=4
[00:03:27.201,751] <dbg> net_if: net_if_tx: (downloader): Processing (pkt 0x200345bc, prio 0) network packet iface 1 (0x200038ec)
[00:03:27.290,161] <inf> dfu_target_mcuboot: MCUBoot image-0 upgrade scheduled. Reset device to apply
[00:03:27.290,161] <dbg> aws_fota: http_fota_handler: FOTA_DOWNLOAD_EVT_FINISHED
[00:03:27.290,191] <dbg> aws_iot: aws_fota_cb_handler: AWS_FOTA_EVT_DL_PROGRESS, (100%)
[00:03:27.290,191] <inf> aws_iot_sample: AWS_IOT_EVT_FOTA_DL_PROGRESS, (100%)
[00:03:27.290,252] <dbg> aws_fota: update_job_execution: update_job_execution, status: 2, version_number: 2
[00:03:27.290,405] <dbg> net_mqtt: mqtt_publish: (downloader): [CID 0x2000b574]:[State 0x06]: >> Topic size 0x0000002b, Data size 0x00000055
[00:03:27.290,466] <err> os: ***** MPU FAULT *****
[00:03:27.290,466] <err> os:   Stacking error (context area might be not valid)
[00:03:27.290,466] <err> os:   Data Access Violation
[00:03:27.290,496] <err> os:   MMFAR Address: 0x20003df0
[00:03:27.290,496] <err> os: r0/a1:  0x00000000  r1/a2:  0x00000000  r2/a3:  0x00000000
[00:03:27.290,527] <err> os: r3/a4:  0x00000000 r12/ip:  0x00000000 r14/lr:  0x00000000
[00:03:27.290,527] <err> os:  xpsr:  0x00000000
[00:03:27.290,557] <err> os: Faulting instruction address (r15/pc): 0x00000000
[00:03:27.290,588] <err> os: >>> ZEPHYR FATAL ERROR 2: Stack overflow on CPU 0
[00:03:27.290,618] <err> os: Current thread: 0x20003cf0 (downloader)
[00:03:27.539,947] <err> os: Halting system

Please help.

Full code: https://github.com/olalonde/ncs-l9-e7/tree/modem-port

I also tried chaning the downloader Kconfig to allow a larger stack size but that didn't solve the issue.