Tumbling Satellite flares every 3-5s

Many times I took pictures of Iridium flares and during my night observations I see hundreds of satellites passing by. However on April 19 around 21UT I saw for the first time a satellite flashing up more then once. I start reading a bit of this phenomena and talked to some people about it and this seem to be a tumbling satellites or tumbling pieces of rockets.

Yesterday, after taken pictures of the ISS I saw at the zenit another tumbling satellite which I was able to photograph. Unfurtunately, setting was already done for Jupiter and Moon, so no ideal picture. The passing happened from South-South-East towards North-North-West at exactly 21h05m35s at the Zenit. Enlarging the picture shows the satellite trail broken 2 times during and exposure of 10s. This means the flares happen between 3-5s. I looked into different databases with no real outcome but this is a potential list of tumbling satellites :

- Iridium 90
- IGS 5A
- Cosmos 1356
- SL-16 R/B
- Iridium 911Tum