That warm feeling that you contributed to the community when you find your bug report in an official release notes 🙂 There is a new firmware release EdgeRouter ER-8/ERPro-8/EP-R8: Firmware v1.9.1 that reports as fixed an issue first reported by me for the 1.9 firmware.
The issue was reported in the thread Update to 1.9 broke my l2tp/ipsec
After some time I even posted a partial solution that was discussed also in that thread: EdgeRouter: Force add the default routes to the load balanced WAN interfaces
It seems that the UBNT support team finally found a permanent fix and released it as part of 1.9.1 EdgeMAX EdgeRouter software release v1.9.1
The part from the release report referring to my issue:
[LoadBalancing] Fix bug when L2TP interface lost connectivity in load-balancing scenario because connected routes got deleted from load balancing routing tables. Discussed here
I still need to deploy the release on all my routers and check it myself.