Tested it on my side and everything is perfectly working fine.
Here are some configurations and screenshots:
1. Configuration without pre-shared key
2. Configuration via Certificate
3. Configuration with pre-shared key
I am not able to replicate this issue of yours. My suggestion is to try re-flashing the firmware of the RUT240 you are having without keeping your settings. Then reconfigure L2TP and IPSec again. If still, you are having the same issue try updating your Windows OS.
Let me know the results.