(solved)sonar 7 external insert some problems

Hi.

I'm using sonar 7 PE

I have RME hdsp 9632 spdif connected to my Lexicon MX 200 spdif.

I have created a bus, and inserted external insert plugin and selected the routings correctly.

I can send signal to Lexicon, and there's signal coming back, but for some reason it's coming back with metallic echo to it.
I can hear the lexicon effect working.
I've tried to adjust the manual offset, with no audible result. The delay meter is showing of delay of 4 ms.
I've bypassed the effects from lexicon, and the signal coming back is still having this metallic echo into it.

I've tried adjust the rme's inputs/outputs & other settings, with no luck.

I'm thinking of somekind of feedback loop somewhere, but I can't figure out what to do.

Any help, please ?