[strongSwan] "no peer config found" but it's all there. What's wrong here?

[Jakob Curdes]

I have been looking at this for hours, can't see the problem.
StrongSwan 5.0.1 on CentOS, older SARIAN router as peer, PSK setup.
Tries to connect, finds proposal for IKE, and then:

charon: 06[CFG] looking for pre-shared key peer configs matching 
a.b.c.d...w.x.y.z[kr05]
charon: 06[CFG] peer config match local: 1 (ID_ANY)
charon: 06[CFG] peer config match remote: 0 (ID_KEY_ID -> 6b:72:30:35)
charon: 06[CFG] ike config match: 1052 (a.b.c.d w.x.y.z IKEv1)
charon: 06[IKE] no peer config found

The config looks like:
    authby=secret
    keyexchange=ikev1
conn krumm-wea5
     left=a.b.c.d
     leftsubnet=10.100.101.0/24
     right=%any
     rightid=kr05
     rightsubnet=172.16.29.0/24

So it sees the ID but claims it is different or what?
As soon as I remove the ID from the sending peer, it finds a config,
but we need the IDs to distinguish different peers with dynamic IPs.

How can I find out more about the reason it says "no peer config found"?

Thank you for a hint,
Jakob