l2tp-in-server disappears

Hello,

I have a problem with RB1100AHx4 with L2TP/IPSEC server. After some time of working normally, the l2tp-in-server in IP/IPSec/Peers simply disapppears and so the new connections are not possible any more. Existing active connections work until the user disconnects. The “solution” is to disable the L2TP server and enable it again, after this the l2tp-in-server appears again and everything works again.
The same happening with different RouterOS versions (started with 6.x) and also the latest 7.16 shows the same symptoms.

Any ideas?

Thanks