As some others, I experience sporadic hang-ups with my EdgeRouter X, like once in every 2-3 days. I'm running OpenWrt 19.07.5. I've tried a few troubleshooting steps, like disabling NAT software/hardware flow offloading, without any luck.
Some people reported that upgrading the bootloader may help. That however would require going back to the stock firmware and then flashing OpenWrt from scratch.
My bootloader is
U-Boot 1.1.3 (UBNT Build Version: e50_001_1e49c) (Jul 27 2018 - 04:44:52). This string can be found inside
router.mtd0.bin file which can be downloaded with Luci at
Save mtdblock contents,
I wonder if someone with a stable EdgeRouter X could share their bootloader file, so I could try flashing it with
mtd. That'd be greatly appreciated. The bootloader can be downloaded via Luci as above.