@emils nice that this problem is allready known.
in my case below is the relevant part of the config :
/ip pool
add name=dyn-vpn ranges=192.168.88.2-192.168.88.19
/ppp profile
add change-tcp-mss=yes dns-server=192.168.88.1 local-address=192.168.88.1 \
name=ppp-in only-one=no remote-address=dyn-vpn use-encryption=required \
use-ipv6=no use-mpls=no
/interface l2tp-server server
set allow-fast-path=yes authentication=mschap2 default-profile=ppp-in enabled=yes ipsec-secret=SERVERPASS max-mru=1460 max-mtu=1460 use-ipsec=yes
/ppp secret
add name=dynuser1 password=DYNUSER1PASS profile=ppp-in
this creates a dynamic ipsec peer as in the documentation ( https://wiki.mikrotik.com/wiki/Manual:Interface/L2TP )
It worked nice until ros 6.43.12 but in 6.44 I get “parsing packet failed, possible cause: wrong password”