I've noticed the reboot issue with the BT hub 5a gets substantially worse with the more/larger versions of modules built into the kernel and packages included in the build. One of my recent builds of the master branch with lots of stuff like batman-adv and wpad wolfssl built in resulted in one of my routers taking at least an hour to boot successfully.
So, as rc4 was getting stuck in prolonged reboots at start-up, I had a stab at building a version of OpenWrt 22.03.0-rc4 r19426-2b1941e47d with Luci omitted based on this guide and inadvertently managed to omit lots of modules such as wpad and wireless too from the sysupgrade file, which for all the ones I noticed were missing I've installed from the feeds along with luci, and it boots/reboots pretty reliably so far.