I managed to find out that delay and metro objects are sending out messages at much higher rate than specified. It seems that there is no time sync within libpd. To test this I made a simple patch that's got a metronome sending a bang every 1 second. In Pd it works as expected. In libpd I registered a dispatcher and a bang is coming in every few milliseconds. When I load in the patch into one of pd-for-ios test projects supplied the result is the same. Seems as if the metronome is working without time limit, sending bangs continuously.