I just wanted to state what helped me (twice now). I have the FW XR500-V2.3.2.134-dumaos33-rc14.img on my XR500 (see https://forum.netduma.com/topic/51611-new-xr500-beta-firmware-33535/ for the FW), normally with Hybrid VPN on. After 2 blackouts (hard restart), the Hybrid VPN menu is not loading. I want to note that if I reset my router in this stage, I will normally get this error and it took me quite some time to restore my XR500 (3 hours in the first run). Also, loading a config with VPN off over …/adv_index.htm is not helping here.
What helped me in the 2nd run: Directly after the error with the Hybrid VPN appeared, I’m downgrading the FW to the INTERMEDIARY_FIRMWARE.img. When doing a factory reset and loading the config without VPN setting, then upgrading the FW to RC14 again and setting up Hybrid VPN again. This took me only 30 min last time.
By the way, are you planning on fixing the bug? I wanted to give the XR500 to a friend of mine when my R3 arrives. But he isn’t a computer scientist like me, so I will install the stable version 2.3.2.134 for him