Hi,

At first everything seemed to work. A node on the one end could ping a
node on the other end over the mesh-network. The ping was hopping from
node to node as expected.

But sometimes some paths do not work anymore.

Some nodes can only reach their direct neighbors via a "normal ping". A
ping to a node via one hop does not work. A "batctl ping" does work!

This only happens to parts of the network and is not permanent. If i
wait it will recover, but then the problem appears at another node.

since "batctl ping" works I'd say your mesh works fine - you have a problem in 
your higher layers. Maybe a mac address collision or an ARP timeout ?

Can you provide specific examples we can go through ? For instance, provide 
the batctl ping output to the neighbor in question, the ping error message 
(does it say timeout / host could not be found / etc), a batctl traceroute to 
the neighbor in question and the output of the global translation table.

Are you trying to ping a 'fixed' node or a node that is roaming ?

Regards,
Marek