B One management VLAN locks up after applying any change to config (updated title)

My B One becomes inaccessible via the web interface whenever I “apply changes” to my configuration. This happens even if I have not changed anything in the config, but simply click on “apply changes.” It comes back if I power cycle the router, and then the web page reports “changes applied” as expected.

Traffic continues to pass through the router throughout. The only problem is that I cannot regain access to the router’s control web page.

I access the router via a management only VLAN via wifi. This has worked in this configuration for a long time (I used to run a Balance One with the same network archtecture). The only thing that has changed of late is the upgrade to 8.5.3 (build 6030), so I suspect that is the culprit, but would have expected someone else to have seen this by now.

I saw Martin’s post about a browser cache, but I get this problem with both FIrefox and Edge. Manually clearing the cache does not help either. Also, if I update the router in one browser and then flip back to a window on another browser (that had been working before) that window will now report a timeout. So, I am pretty confident the problem resides with the router and its configuration. Any thoughts?

UPDATE: I have determined that the problem is that my Management VLAN appears to stop functioning after saving changes, but it will resume functioning if I power-cycle the router. Nothing else gets it going. While the VLAN is down, I cannot access the router’s web page. My managed switch and the APs that are on it, also go down. All of those devices live on the Management VLAN. Once I power cycle the router, everything comes back up. I have spent hours poring over this and cannot see anything wrong in the configuration. I have disabled my internal firewall rules and that makes no difference. I have tried wifi and ethernet access to the VLAN and both have the same effect. I also lose internet access from the computer on that VLAN, but other wired devices on other VLANs continue normally.

I gave up and rebuilt the configuration from scratch. I cannot explain what the problem was. It was somehow embedded into a survivable setting that persisted through restoring config files. I went back through a year of back-ups (five or six) to no avail. I am confident it was not part of my settings because the problem had not expressed itself when I made the backups in the first place. Ah well…