strongswan duplicates reqid at times, causing failures with multi-P2
Where a system has a number of P2s on a single P1 with IKEv1, strongswan at times assigns the same reqid across multiple SAs. This can exhibit itself as a pair of P2s where only one of the two functions, whichever has rekeyed most recently. Rekeying one breaks the one with the duplicate reqid.
This appears to be a race condition in strongswan. Possibly this: