How can I store the output value from each for-iterator loop in Simulink?

Here is my problem: I am receiveing packets of data (through WiFi) of 21 frames each. In order to unpack the data I use a for-iterator in simulink which repeats 21 times sliding through the frames. The core of the problem is that apparently, I can only read the last frame at the output of the iterated subsystem. How can I have all the frames?

I have already tried to use the buffer block, but I get the error: Error in 'NaxisWiFi_DataColl_v5/For Iterator Subsystem/Buffer': All sample times must be discrete. No continuous or constant sample times are allowed.

I checked it with the utility Display/sample time/colors and I have only triggered and descrete sample times. I guess there is some compatibility issue with the for loop.

Any suggestion? Thank you very much in advance.